Are motorgliders safer than towed gliders?

[Eric Greenwell]

Recently, Old Bob the Purist wrote:

"Eric, you must admit that convenience and safety go together. What is interesting is the reliability of the motorglider when needed. I can only recall two instances where the motor did not start when called upon that resulted in land outs. Once was during a Seniors event when some guy left an airport area low and was going to rely on the motor and it did not start when called upon and the other there was a malfunction of the engine and it would not start and also resulted in a land out. So with that said I would like for you to give me some idea as to the percentage of reliability that you would put on a motorglider start when needed, I would say that the reliability is probably 98%, which certainly makes it a save your ass safety device. Old Bob, The Purist"

A motor does not automatically give you safety or convenience. For some pilots, the additional complexity and cost of a motor exceeds the convenience of tows when desired, and for others, that complexity decreases their safety when low and under pressure to avoid a landout.

But it's good question: just how reliably does a motorglider start? That's a bit like asking "how reliable is the L/D on your glider", because L/D is what most of us depend on to keep us safe during a flight. The answer to both questions is "it depends"; for example, the type of motorglider, it's maintenance, and pilot ability can all strongly affect the success of an attempted start in stressful conditions (and knowing you will crash if the engine doesn't start is definitely stressful). The older (before the DG400, say) two stroke motorgliders are, I think, worse than 98%, but the modern FES glider is much better than 98%, possibly enough better that many pilots would be safer depending it starting than the safety of a field they pick out from the air.

Using your 98% reliability for starting, I'd expect to have a failed in-flight start about once every 10 years. A crash every 10 years sounds like very poor odds to me! No crashes for me, however, even though I made a lot use of the convenience of my motorglider to enhance my soaring experience, as I maintain my safety because I don't count on it starting to "save my ass". You, on the other hand, would gain neither convenience nor safety with a motorglider, unless you change the way you've been flying the last 5+ years.

[youngbl...@gmail.com]

Eric, I appreciate the compliment that you gave me about flying without a motor, instead of 5 + years please make it 45+ years. Why do you refer to landing out as crashing??? Landing out is not crashing rather an inevitable event as all PURIST must be capable of performing, if you cannot accomplish that objective then you need a motorglider. Even if two stroke engines are less reliable than 98% they offset the purist by whatever percentage you choose to tag them with, remember the purist has zero %.
The pure glider has zero reliability and relies only on sound decision making and pilot performance, we do not have that get me home button, even 50% is better than zero%. Until the time comes that I need a motorglider I will continue to fly my Lowly 27 and give the Big Dogs a run for their money. Old Bob, The Purist

[Eric Greenwell]

_You_ are the one using the phrase "save your ass safety device", implying the pilot will crash if the engine doesn't start. I do not think landing out rises to the "risking your ass" category, as all of us take that risk when the launch is over. Say "risking a retrieve", if that's what you mean. The motor counts as a "safety device" only if the pilot intends to fly where it might be required to avoid a landing that will be a crash with glider damage as a minimum, or fatal as a maximum.

Eric

[youngbl...@gmail.com]

Yes, I did use the term, Save Your Ass", only as a reference to enhancing your flight to look better rather than do the manly thing like being a PURIST and dealing with what you are dealt. Maybe I should just use the acronym, SYAG, or AKA as "Save Your Ass Glider". Old Bob, The Purist

[Glenn Betzoldt]

Ok Bob you said It and opened the door. "Until the time comes that I need a motorglider I will continue to fly my Lowly 27 and give the Big Dogs a run for their money. Old Bob, The Purist"
So my ASH26 is for sail.
GB

[jfitch]

While an off airport landing doesn't guarantee a crash, it increases the odds substantially. There is about a 10x increase in chances of damage in a landing off airport, compared to an airport landing. You can quickly calculate this from the Soaring Safety foundation figures.

[Eric Greenwell]

Please, just stop using "save your ass" unless you mean "avoiding physical injury from a glider crash". It's totally unnecessary to use the phrase and leads to confusion about what you mean because you've been using it in the context of safety; for example, "Eric, you must admit that convenience and safety go together."

[youngbl...@gmail.com]

Eric, SYAG is like putting lipstick on a pig, it is still a pig regardless of how you dress it up. Don't take this thread so serious, Fitch seems to have this discussion in the right frame of mind. I was hoping that Bud Light would have a motorglider on their new can, it might just get them out of a deep hole. So, here we are getting into spring around the country and those motorgliders are coming out of the trailers, I am sure that none of them will be late for dinner this year.
On another note the SSA was very kind to us here on the Treasure Coast and sent John Godfrey over to Fly-In-Ranches, AKA FD25 to install a OGN system that is a nice compliment to soaring activities here in South Florida, thanks John and Davis, the system is helping us keep track of our gliders that are flying our challenging triangles deep into the Everglades.
I have flown my Lowly 27 a few times this spring, threaded the needle a few times and made my 5th trip around Lake O, without a motor. It is also important to notice that the SYAG's at Seminole have been flying a few nice triangles this year as opposed to past years, I guess we must be putting the pressure on the SYAG's!
The mango orchard is looking good, the finally needed rain has arrives and the fruit is looking good for a June and July harvest, I will have a box headed your way as soon as they are ready to ship. OBTP

[2G]

A long time ago I listened to Tom Knauff talk about a record flight he had made in the Adriondacks the previous season. At the last stretch of the flight back home he was joined by 3 other gliders. It was late in the day, of course, and lift was scarce. They encountered a heavily forested stretch with no possibility of land out whatsoever. ALL of them ventured on w/o anyone saying on the radio that this is stupid, or questioning the wisdom of this reckless move. They were just silent. Well, one of them found a weak thermal and they all climbed up and made it home. If this thermal had not been found ALL of them would have gone down into the trees, with a high probability of a fatality by at least one of them. No one in the audience, including me, questioned Knauff's decision-making, perhaps because it was in the past. But, here you have a nationally-recognized authority on glider instruction and safety admit to one of the most reckless and dangerous examples of glider flying that I have ever heard of. While he had the possibility of setting a world record, the others didn't. And even a world record is NOT worth dying over.

Landing out is inherently risky (with the possible exception of a large, flat, plowed field) as you can't possibly see all of the potential hazards from even pattern altitude. One should expect some kind of damage once in every 10 landouts. With a motorglider, the landout is a backup to the motor. If motor failure is on the order of one in a hundred, then you could expect damage in one out of a thousand restarts (10 times 100). A typical pilot will likely never encounter this as I typically do one restart a year.

Tom

[Eric Greenwell]

I don't know what the restart rate is for "typical" motorglider pilots, but I restart 5+ times year, and when I flew towed gliders, I'd land away from home a few times a year. I know how to cut that number down to one (or even none, like OBTP), but it means flying so conservatively, I wouldn't have as much fun as I do now. How often do you other motorglider pilots restart? Piston, rotary, jet, electric - I'm interested in replies from all pilots.

[Eric Greenwell]

While the average might be 10X, I'm sure there are large variations, depending on the flying area and the pilot, and those are some reasons we can not conclude the motor is a "safety device". I can't think of any way we can estimate the outcome of every pilot being equipped with a motor. I suggest the results might be worse, not better, for a number of reasons. Some are...

* pilots may fly much more aggressively, increasing the number of times they are faced with an outlanding, and the number of failed starts will be larger
* the fields they pick may not be as good as they are now, if they think the motor will save them, increasing the 10x to say 15x or more
* there will be more launch accidents, as the motorglider pilots will not be as experienced as the tow pilots

[youngbl...@gmail.com]

Eric, you certainly look at things through rose colored glasses, the only thing about me are my political views and my appreciation for the dollar! You may find many people among this group that know me and have flown with me many times and I am sure they will certainly correct you on the flying of OBTP, who else would roll the Pawnee??? You can go to Soaring Forum Group on Facebook and see it yourself. Old Bob, The Purist

[youngbl...@gmail.com]

Should have said the only conservative thing about me.

[Eric Bick (DY)]

This, to me, is an interesting question Eric G. raises. I am on my 3rd motorglider. In order, they are an ASH 26E with Wankel rotary engine, Carat A, with Sauer 4-stroke engine, and now a DG808C with a Solo 2-stroke engine. In the ASH 26E I had 71 flights; in the Carat, 42; in the DG808C, only 3 since purchase.

Flying the ASH 26E, the only time, other than one, I did air restarts was to check that the system was working. The only time I needed it to keep from landing out, it would not start due to a sticky microswitch. Both the mast extended and retracted lights were green and the default logic was apparently do nothing, even though I could see the fully extended mast. I flew the ASH like a motorless glider, assuming the engine would never start when needed. The time it would not start when needed, I had already picked out a plowed field for outlanding, and I had a thousand feet of altitude to try different options before committing. The only one I didn't think of was doing a windmill start. I don't know whether that would have worked or not. It might be the prop rotating would have unstuck the stuck microswitch and all would have been good for getting back to the airport. So, in the ASH, one attempted air restart out of 71 flights.

The Carat is a completely different machine. The engine is a bored-out VW air-cooled, 4 cylinder gem. I found it to be super reliable. I also found that I was aggressively pushing the envelope, relying on the engine reliability for starting right up rather than having a safe outlanding site within glider. A couple of times, flying over unlandable terrain with no escape should the engine quit, I had to remind myself that this was really dumb. The times I needed an air restart, it always started. It was so easy to fly, there were times I started the engine just to make sure that is was running if I might need it. Always started up to 16 kft MSL and subzero temps. Out of my 42 Carat flights, how many restarts did I need to avert a landout? Maybe 2.

The DG with its Solo engine is another breed of cat. I will be flying it like the engine is going to self-destruct at any time (gross hyperbole). The Solo users group demonstrates that there are any number of mechanical and electrical issues with these engines and the 800 model line. However, many of those issues occur on the ground, not in the air, and prevent a self-launch. In such a case, I can generally take an aerotow. In each of my first three flights, the engine has been flawless in self-launch, and I've done air restarts each flight with no issues. But, I will be flying the glider this first season as if there is no engine available for self-retrieve.

In going from the ASH to the Carat, I made a reliability/performance trade, giving up considerable glide performance in the ASH for high reliability in the Carat. I found that, for me, this was a different type of soaring in the Carat as to style and mindset. It was absolutely too easy to stop worrying about finding a thermal, and start the engine and motor away - something I never did in the ASH, and won't do in the DG. Soaring is about finding the lift, staying up, and going places, not about using the engine as a crutch. As much as I loved the Carat and its actually quite good glide performance, I found I wanted to go back to the basics of soaring, which means emphasizing the self-launch capability of a motorglider from wherever, whenever, regardless of tow availability, and, after retracting the engine, soaring as if there is no engine behind me. I also like the idea that if I have to landout at another airfield due to weather or whatever, I can relaunch myself without having to get the trailer or a tow plane from the home field.

[2G]

I was referring only to away-from-airport restarts where the only other option is an off-field landing. I probably also restart half a dozen times near the airport.

Tom

[2G]

I don't have hard data to back this up, just personal experiences and those of others. Obviously there can be a great variation between pilots and where they fly.

> * the fields they pick may not be as good as they are now, if they think the motor will save them, increasing the 10x to say 15x or more
> * there will be more launch accidents, as the motorglider pilots will not be as experienced as the tow pilots

That is totally unsupported. Many motorglider pilots ARE also tow pilots, as well as airline and military pilots. A towed glider launch is inherently more complex and hazardous than a motorglider launch. I know of several tow pilots who have been killed by a kiting glider but know of NO motorglider pilots killed during the launch.

Tom

[jfitch]

On Saturday, April 15, 2023 at 11:50:05 AM UTC-7, Eric Greenwell wrote:

This is my 23rd year with the motorglider, I think I have restarted (to avoid an away-from-home landing) 6 times. All of them over the pattern of a large airport listed on the sectional. Yes I fly conservatively, but I go the same places others go, I just stay higher. I started it maybe 10 or 12 times in that 23 years to avoid a relight, usually before the engine is even stowed. It has failed to start exactly once, first start after winter layup on the ground.

One thing about motorgliders is they are more complex than towed gliders, and require perhaps 3 or 4x the maintenance. In my experience glider pilots - many of them at least - are not very good at maintenance. That makes those pilots possibly dangerous in a motorglider, certainly if they are depending on the engine.

[Join ASA]

Different pilots will fly differently than my "average" pilot. That is not in question. Eric Bick had a failure to start in his first off-field situation, which falls into the "shit happens" category. The point that I was making is that the imagined unreliability of motorgliders is not going to make you more unsafe. In fact, motorgliders will reduce the probability of a bad outcome.

Tom

[Eric Greenwell]

On Saturday, April 15, 2023 at 5:23:44 PM UTC-7, 2G wrote:
> On Saturday, April 15, 2023 at 12:07:58 PM UTC-7, Eric Greenwell wrote:

...

> > > While an off airport landing doesn't guarantee a crash, it increases the odds substantially. There is about a 10x increase in chances of damage in a landing off airport, compared to an airport landing. You can quickly calculate this from the Soaring Safety foundation figures.
> > While the average might be 10X, I'm sure there are large variations, depending on the flying area and the pilot, and those are some reasons we can not conclude the motor is a "safety device". I can't think of any way we can estimate the outcome of every pilot being equipped with a motor. I suggest the results might be worse, not better, for a number of reasons. Some are...
> >
> > * pilots may fly much more aggressively, increasing the number of times they are faced with an outlanding, and the number of failed starts will be larger
> I don't have hard data to back this up, just personal experiences and those of others. Obviously there can be a great variation between pilots and where they fly.
> > * the fields they pick may not be as good as they are now, if they think the motor will save them, increasing the 10x to say 15x or more
> > * there will be more launch accidents, as the motorglider pilots will not be as experienced as the tow pilots
> That is totally unsupported. Many motorglider pilots ARE also tow pilots, as well as airline and military pilots. A towed glider launch is inherently more complex and hazardous than a motorglider launch. I know of several tow pilots who have been killed by a kiting glider but know of NO motorglider pilots killed during the launch.
>
> Tom

My list described pilots who are _not_ motorglider pilots now. The demographics of these pilots is likely younger and less experienced in all aircraft, compared to current motorglider pilots.

[Eric Greenwell]

On Saturday, April 15, 2023 at 5:15:40 PM UTC-7, 2G wrote:
> On Saturday, April 15, 2023 at 11:50:05 AM UTC-7, Eric Greenwell wrote:
> > On Saturday, April 15, 2023 at 11:13:54 AM UTC-7, 2G wrote:

...

> > I don't know what the restart rate is for "typical" motorglider pilots, but I restart 5+ times year, and when I flew towed gliders, I'd land away from home a few times a year. I know how to cut that number down to one (or even none, like OBTP), but it means flying so conservatively, I wouldn't have as much fun as I do now. How often do you other motorglider pilots restart? Piston, rotary, jet, electric - I'm interested in replies from all pilots.
> I was referring only to away-from-airport restarts where the only other option is an off-field landing. I probably also restart half a dozen times near the airport.
>
> Tom

My numbers are for all restarts away from the home airport: most are over an airport, perhaps two a year over a field.

[youngbl...@gmail.com]

Eric, there is no doubt about the safety of a motorglider vs a towed glider, the SYAG offers a safety factor just by the engine itself that the towed glider does not have. The only exception to this would be the sustainer SYAG and not the self launch. The sustainer still relies on a tow whether it is aero, winch or auto, and that in an of itself is much more challenging than a self launch. As a past tow pilot you should certainly be cognizant of the possible issues during towing, especially having a solo first time glider pilot at the end of your rope, I still do 99% of the tows at our club and I do continue to be vigilant and evaluate most every person that I tow, and there are times when the words on the ground are not very kind, I guess at my old age has made me a bit less tolerant.
I have watched self launch SYAG's take off and get airborne and it has been quiet impressive in most cases unless the SYAG has a solo engine especially in a duel seat, those dinosaurs are to say the least quiet anemic.
I would really like to ask the question about motorglider accidents and if the motorglider pilot was so much more experienced than other glider pilots do the accident numbers reflect that? Old Bob, The Purist

[jfitch]

I think we need a nice acronym for the motorless towed gliders, as a counterpoint to Old Bob's SYAG. How about SG for Suicide Glider? After all, in one of those things, what do you do when the wind quits? And aren't you depending on a (minimum) 50 year old PA-25 to get it off the ground? What else would you fly 300 km over alligator infested swamps never getting above pattern altitude?

[Ido Millet]

Here is a spreadsheet with narrative details of 21 motorglider accidents involving engine reliability/performance problems in the last 14 years:
https://www.milletsoftware.com/Download/Motor_Glider_Accidents_with_Engine_Problems_2008_2022.xlsx

I extracted the data from my USA glider accident web pivot charts at:
https://www.milletsoftware.com/Data/Glider_Events.html

In total, there were 75 motorglider accidents during that time frame.
So engine reliability/performance issues make up 28% of motorglider accidents.

[jfitch]

Stated more properly, misplaced pilot expectations of engine reliability/performance issues contribute to 28% of motorglider accidents. "One must always be prepared for the possibility that the engine will not provide the hoped for propulsion". Verbatim from the ASH operator's manual. In your research, did you find many cases (or even one) of the presence of an engine by itself directly causing an accident? I know of none. On the other hand, I have has several friends die or nearly die in a SG, trying to make in home to avoid an inconvenient retrieve. A SYAG will largely eliminate that risk. Maybe the acronym should be SYFIR - Save Yourself From an Inconvenient Retrieve. I'll start using that instead.

[youngbl...@gmail.com]

Fitch, I would love to sit at the bar and have a few drinks with you, we would both walk away with an appreciation for each other. Eric continues to berate my flights into the swamp and always thinks that I make it back home, it is not true, he just overlooks things, something I would not expect from an engineer like Eric. That 28% is a big number, us purist could never reach 28%, we could not even reach 1%, so that puts is a a much better class of statistics than the SYAG guys.
Hope things are good up there in the liberal land, things down here in Trump land are quiet well. Old Bob, The Purist

[jfitch]

Old Bob, 28% is a big number compared to what? 28% of what? What I do know is that 100% of SG crash because they don't have a motor. Prove me wrong: every one that crashes doesn't have a motor. Giving a percent probability without citing the reference class is a favorite of serial statistical liars, most notably the pharmaceutical industry and politicians.

I'll drink a beer with you but not in steamy Florida, land of DeSantis. I'm currently enjoying 41 deg and rain, here in the lib PNW.

[youngbl...@gmail.com]

Perfectly legit statement, if a pure glider crashes then it doesn't have a motor, true! Not having a motor is not the cause of the crash, just a factual statement something like , "It Crashed Without a Motor".
Yes, 41 degrees sounds nice but without the rain would be much nicer, I doubt that we will see 41 degrees again until 2024.
If by chance I see DeSantis at our local republican headquarters I will get a selfie for you and try to get you an autographed pic as well. Keep the progressive liberals funded up in the PNW, don't order Bud Light when you stock the boat for the annual trip to Alaska. Old Bob, The Purist

[2G]

I reviewed every MG accident listed in this compilation and found that the vast majority of cases to be pilot error. A couple were the direct result of bad maintenance. And a couple more involved home-builts, which are not relevant to this discussion.

It is extremely important to recognize that engines are only a CONVENIENCE, and should not be viewed as a LIFE-SAVING DEVICE. Motors (even electric ones) sometimes don't start, although they do 99+% of the time (if properly maintained). This includes well-maintained Pawnees.

Case 1: "attempted an emergency landing in rocky, hilly terrain"
Conclusion: Pilot error
Case 2: "Lacking the altitude to return to the airport, the pilot chose a road for a forced landing."
Conclusion: Pilot error
Case 3: "There were about 2 ounces of oil drained from the oil bath reservoir. "
Conclusion: Pilot error
Case 4: " The inspection did reveal damage to the cylinder walls"
Conclusion: Undetected engine damage
Case 5: "The pilot departed in the self-launching motorized glider for the local flight. He stated that it was a smooth day with no lift, and he had to use the engine several times in order to stay aloft. While returning to the departure airport, at approximately 1,000 feet, the pilot raised the engine and attempted to start it. He received a battery warning indication in the cockpit and was unable to start the engine with the electrical system. The pilot selected a field for landing, but continued to troubleshoot the engine. The pilot successfully restarted the engine, abandoned the landing approach and flew for an additional few seconds before the engine stopped again and the pilot executed a forced landing to a second field. He stated that he was not properly configured to land and landed hard, which resulted in substantial damage to the glider's fuselage."
Conclusion: Pilot error
Case 6: "A witness reported that the motorglider engine did not sound normal during the preflight run-up and takeoff. The engine subsequently lost power when the aircraft was about 200 feet above ground level."
Conclusion: Pilot error
Case 7: "Using the taxiway as the runway, the pilot of the self-launching motor glider began the takeoff; however, the glider did not gain sufficient airspeed to depart. The pilot elected to continue the ground roll to an overrun area in order to give room for other gliders to depart."
Conclusion: Pilot error
Case 8: "The pilot reported that on the day of the accident the weather was marginal, with low clouds and shifting wind. He took off in the motorized glider and then stowed the engine. About 1 mile northwest of the airport, the pilot realized that the wind was not conducive to convective activity, and the glider started to descend. The pilot turned back toward the airport and extended the engine/propeller to restart the engine; however, the engine would not start. The pilot entered the downwind leg of the traffic pattern and lowered the landing gear. As the pilot was turning from the downwind to the base leg of the traffic pattern, the left wing of the glider stalled; the glider subsequently impacted the ground and cart-wheeled before coming to a rest in a field. The pilot reported that there were no preimpact mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation. The pilot reported that he believed the accident occurred because 'everything happened so fast,” and he was unable to use a checklist."
Conclusion: Pilot error
Case 9: "The pilot reported that the motor-glider was on a long, straight-in visual approach to land when he heard a very loud 'bang' in the front of the motor-glider followed by a severe vibration. The pilot shut down the engine and made a forced landing to a field. A postaccident examination of the aircraft revealed that the flexible disk on the front of the driveshaft had disconnected. Only one of the three bolts that connected the disk to the driveshaft remained partially installed. No evidence of Loctite or torque paint was found on the bolt. The bolt's threads were rusted, and the bolt's head was digging into the gearbox housing. The second bolt was sheared off, and the third bolt was missing.

A review of maintenance records revealed that the motor-glider's most recent annual inspection was completed about 1 month before the accident. According to the manufacturer's maintenance manual, a mechanic was required to check the tightness of the bolt connections of the flexible disk on the front side of the drive shaft. It is likely that the mechanic improperly inspected the bolts that connected the flexible joint to the front side of the driveshaft during the last annual inspection, which resulted in the ultimate failure of these components.

The maintenance records also revealed that, during the last annual inspection, Federal Aviation Administration Airworthiness Directive (AD) 2006-19-08, which required inspection for deformations and cracks in the exhaust pipes and the replacement of any damaged exhaust pipes found, had not been properly complied with when a weld repair was made to the No. 1 exhaust pipe. The mechanic's failure to not properly comply with the AD and the operator's failure to ensure that the AD was complied with were not causal to the accident; however, because the AD was not complied with, the motor-glider was not considered airworthy.
Conclusion: Improper maintenance
Case 10: "About 20 miles from the departure airport, the motor glider began losing altitude due to a loss of thermal lift, and the pilot then prepared for an off-airport landing. He deployed the retractable engine and attempted to start it but was unsuccessful. The pilot set up for landing to a field. He did not see power lines bordering the approach end of the field, and the motor glider impacted the power lines and then descended to the ground in a nose-down attitude.
Conclusion: Pilot error
Case 11: "The commercial pilot was conducting a personal cross-country flight. The pilot reported that, while en route to the destination airport, he noted that the right tank's fuel level was not changing and that it did not appear that fuel was draining from the right tank. The fuel remaining in the left fuel tank was not adequate to complete the planned flight. The pilot chose to divert to a closer airport, and while he was preparing to land, the engine lost power. The pilot performed a forced landing to a field, during which the airplane nosed over and came to rest inverted."
Conclusion: Pilot error and this involved a TMG (touring motorglider)
Case 12: "The sport pilot of the experimental, amateur-built motorglider"
Conclusion: Home built glider - not relevant
Case 13: "After gliding for about 2 ½ hours cross-country, the motorglider began to encounter reduced lift conditions. The private pilot intended to start the engine so that he could return to the departure airport under powered flight but also identified a nearby field for landing in case the engine did not start. As the glider overflew the field, the pilot extended the propeller and attempted three times to start the engine; however, it did not start. With limited altitude, increased drag from the propeller and mast, and an unanticipated headwind, the glider was unable to reach the landing target and impacted trees, resulting in substantial damage."
Conclusion: Pilot error
Case 14: "The airline transport pilot was conducting a local flight in his motor-powered glider. The pilot had the right fuel tank selected and was flying in a counterclockwise direction around a ground reference point when the engine began to lose power. The pilot switched fuel tanks with no improvement and selected a nearby road for a forced landing. During the landing roll on the ice-covered road, the glider's left wing impacted a bush, and the glider exited the road; the nosewheel broke off when it impacted a ditch.
Based on the available data, it is likely the fuel unported during the glider's climbing turn, which resulted in fuel starvation and the loss of engine power.
Conclusion: Pilot error and TMG (not relevant)
Case 15: "He reported that, about 4 miles from the airport, the glider began to sink about 1,000 ft per minute. He attempted to restart the engine but was unsuccessful in the limited time available. He chose a field for an off-airport landing, the glider touched down, but the ground was slightly uneven, which resulted in the right wing dragging. The glider veered 20° to the right before coming to rest.

The glider sustained substantial damage to the horizontal stabilizer and elevator.
Conclusion: Pilot error - attempted a restart at too low of an altitude.
Case 16: "The airline transport pilot reported that, during a cross-country flight and while climbing toward a mountain pass, the experimental, amateur-built motorglider's engine began to overheat."
Conclusion: Home-built, irrelevant
Case 17: "The powered-glider pilot reported that, during the return flight to the airport after an informal glider competition, about 10,000 to 11,000 ft over mountainous terrain, he was unable to find lift, the glider descended to 9,000 ft, and he started the sustainer engine. He added that, after the glider climbed back to the initial altitude, he shut the sustainer engine off, stowed it, and continued to the destination airport.
Conclusion: WTF! This is expected behavior!!
Case 18: "The private pilot of a motor glider was taking off when he noticed the engine sounded 'a little rough'; as he turned downwind, he started to smell smoke. He reported that he shut down the engine and returned for an uneventful landing. When the motor glider stopped, the pilot noticed flames below the right door; the flames grew and eventually consumed and destroyed the airplane. Postaccident examination of the wreckage revealed that the exhaust manifold had various cracks on the tubing. Examination of the exhaust manifold revealed the fracture and cracking of the exhaust system manifold tubes was due to fatigue. The fatigue cracks on the exhaust manifold were progressive in nature and had likely been present for some time before the accident, allowing exhaust gasses to begin escaping into the engine compartment before reaching the muffler assembly. It is likely that the exhaust gases caused a flammable condition the that resulted in a ground fire after landing"
Conclusion: Improper maintenance
Case 19: "The pilot was conducting a personal flight in an electrically-powered, self-launching motor glider. He stated that, while returning to the departure airport at the conclusion of the flight, the glider encountered sink and he turned on the electric motor, but it produced “no thrust.” The glider continued to descend and impacted a house about 2 miles from the airport, resulting in substantial damage. The pilot reported that there were no mechanical failures or malfunctions with the glider that would have prevented normal operation before the accident and that the accident might have been prevented with “better management of power and understanding of battery power source.”
Conclusion: Pilot error
Case 20: "The pilot subsequently made a forced landing and the airplane impacted a fence about 1.5 miles short of the runway. The glider sustained substantial damage.
Postaccident examination of the glider revealed that both propeller blades and the propeller control knob were in the feathered position. Examination of the engine and airplane revealed no mechanical deficiencies that would have precluded normal operation at the time of impact."
Conclusion: Pilot error and a TMG
Case 21: "The pilot, who is also the designer and builder of the experimental motorglider"
Conclusion: Home-built, irrelevant
Case 22: "After departing on a local flight, the pilot of the motor glider crossed a ridge line into a valley at an altitude of about 8,000 ft mean sea level, and then glided to the south in search of lift, but was unsuccessful. He decided to land on a brown, flat, field that appeared to be recently tilled. The pilot set up for a landing, and then deployed the glider's sustainer engine. The engine did not start, so he continued his approach to land. During the landing, the right wing struck the ground, the glider ground looped, and was substantially damaged. The flight manual for the sustainer engine advised that, the sustainer engine should only be extended and started when there was suitable terrain for landing within gliding distance, and furthermore, below 984 ft above ground level, starting attempts were to be avoided 'so as to have a safe height left for planning the approach pattern should the engine fail to run!' The pilot stated that there was no mechanical malfunction or failure with the glider, and that he would recommend trying to start the sustainer engine at a higher altitude.
Conclusion: Pilot error

[jfitch]

I note that in 12 of the 22 cases cited, the crash was the result of a bad choice of off field landing site, or a poorly executed off field landing. The engine was only incidental. This could (and does) happen in an SG as well. One can argue that the pilots were lulled into complacency, thinking that the engine was their "get out of jail" card. That fits the description in some of the cases, in others, the pilot had a field selected but crash landed anyway.

[Ido Millet]

2G, you seem to summarized the data in a somewhat "selective" way.
For example, you state "Case 1: "attempted an emergency landing in rocky, hilly terrain."
The complete sentence is: "pilot was unable to restart the engine and attempted an emergency landing in rocky, hilly terrain."

Perhaps the following can serve as a less "selective" summary:
______________________________________________________________
1 The private pilot was unable to restart the engine and attempted an emergency landing in rocky, hilly terrain.
2 The pilot of the powered glider stated that about 30 seconds after takeoff, about 170 feet above the ground, the engine rpm decreased.
3 ... in cruise flight at 1,800 feet when the motorized glider experienced a total loss of engine power. He attempted an engine restart with negative results and made a forced landing.
4 ...experienced a partial loss of engine power on takeoff and landed hard while attempting a go around.
5 ...received a battery warning indication in the cockpit and was unable to start the engine with the electrical system.
6 The engine subsequently lost power when the aircraft was about 200 feet above ground level.
7 the pilot of the self-launching motor glider began the takeoff; however, the glider did not gain sufficient airspeed to depart.
8 The pilot turned back toward the airport and extended the engine/propeller to restart the engine; however, the engine would not start.
9 ...heard a very loud 'bang' in the front of the motor-glider followed by a severe vibration. The pilot shut down the engine and made a forced landing to a field.
10 He deployed the retractable engine and attempted to start it but was unsuccessful.
11 ...while he was preparing to land, the engine lost power.
12 after takeoff, the primary engine experienced a total loss of power about 75 ft above ground level, and the secondary engine was unable to maintain the motorglider's altitude.
13 As the glider overflew the field, the pilot extended the propeller and attempted three times to start the engine; however, it did not start.
14 The pilot had the right fuel tank selected and was flying in a counterclockwise direction around a ground reference point when the engine began to lose power. ...it is likely the fuel unported during the glider's climbing turn, which resulted in fuel starvation and the loss of engine power.
15 ...while climbing toward a mountain pass, the experimental, amateur-built motorglider's engine began to overheat. The pilot delayed the climb to allow the engine to cool down and continued toward the pass, which resulted in reduced terrain clearance. As the motorglider approached the pass, it encountered a downdraft, and the engine was unable to produce enough power to stop the descent.
16 ... 4 miles from the airport, the glider began to sink about 1,000 ft per minute. He attempted to restart the engine but was unsuccessful in the limited time available.
17 ... was taking off when he noticed the engine sounded 'a little rough'; as he turned downwind, he started to smell smoke. He reported that he shut down the engine and returned for an uneventful landing. When the motor glider stopped, the pilot noticed flames below the right door; the flames grew and eventually consumed and destroyed the airplane.
18 the glider encountered sink and he turned on the electric motor, but it produced “no thrust.”
19 The engine started but was not producing the expected power. The pilot thought he had a fuel problem and was not aware that the propeller was still in a feathered condition.
20 The pilot, who is also the designer and builder of the experimental motorglider, was making his second flight after having completed a number of high-speed taxi tests ... On the accident flight, immediately after takeoff, the pusher-configuration engine again lost power from 6,500 rpm to approximately 4,300 rpm.
21 The pilot set up for a landing, and then deployed the glider's sustainer engine. The engine did not start, …
__________________________________________________________________

Asking "who's at fault: the pilot or the engine?" does not address the subject of this thread: "Are motorgliders safer than towed gliders?"
We can't answer that question with certainty. But we shouldn't ignore anecdotal data that points to the need for extra vigilance.

[Dan Marotta]

Well, you could look at accident RATES rather than NUMBERS. I would bet
the rates are higher for motor gliders but I'd also bet that the higher
numbers are due to higher complexity and, possibly, pilots who are not
always capable of handling the additional complexity.

I currently own a motor glider which I've flown almost 1,000 hours and
previously six pure gliders. I have not had an accident in any of them
so, by applying a lot of the "logic" which is so prevalent on this
group, they are of equal "safety".

Dan
5J

[2G]

When someone pontificates and includes the words "I will bet" I immediately know that what they have to say is worthless and that they have done ZERO research to back up their opinion.

Tom

[Jason Leonard]

Ask Pat Costello why our premiums are higher than pure gliders. They have the data and told me directly.

I've had 1 failure on takeoff, and 2 failed air starts. On takeoff I always climb inside of engine extended glide of either the home airport or a safe landing site. Where I fly out of; that means the home airport, basically.

One air start attempt failure was due to a failed stator to magneto. The magnets degraded and fell off of the magneto and bound in the stator, blocking the engine. The 2nd failed air start was during SLS training. The student did not hold target speed closely enough, and oversped the extending engine mechanism. We landed with the engine extended at our home air field. Both cases the glider was kept inside of glide of Treasure Coast Motorglider Club.

I've used the engine to fly on days others packed up and went home. I had a blast and got to enjoy myself and learn. Instead of learning an inconvenient lesson: I learned an OLC points lesson. In other words: no harm and I got to fly in more challenging conditions (higher winds) and it even taught me to be even more aware of which way I'd land at each field should I need them. Before I just knew fields were available, and learned to rule certain fields out due to direction of wind if it's high velocity.

Aside from the unreliability of the motorglider, I love it. If only I had a more pure way to launch my DG500..............

[jfitch]

And yet everything I said in my post still stands. In most cases, the glider did an off field landing. In most cases this was avoidable, or if not avoidable, identical to a situation with a towed glider that has a broken rope or has run low on altitude. If the engine played a roll, it was to make the pilot complacent, or distract him/her when they should have been landing the aircraft. Pilots susceptible to complacency or distraction should probably not own a motorglider (or perhaps any aircraft), that is a human psychology problem, not a motorglider problem.

Regarding insurance premiums being higher for motorgliders, it has not been the case for me. The premium represents the value of the glider, which is substantially higher in a motorglider. The premium rate ($/insured $) is actually a bit lower than my last towed glider.

[2G]

I very clearly stated up front that the reliability of the motor IS NOT to be used in a life threatening situation. Thus, when piloting a MG, you should ALWAYS have a safe landing spot within gliding distance. Obviously in Case 1 they DID NOT and an accident resulted. The same goes for a pure glider, BTW, which makes the safety aspect identical.

Most of the time (99%+) the motor will start, but I wouldn't want to bet my life on 100 to 1 odds.

Tom

[Dan Marotta]

"I will bet" you think everything you say is correct, eh, Tom?

I stand by what I said: Rates, not Numbers, and there are a lot of
"pilots" out there that are in way over their heads. That's an opinion,
but I'll stand by that one, too, based on decades of observation

Dan
5J

[Dan Marotta]

Oh, I just reread your previous reply to me and I want to point out that
I am a HE, not a THEY. What a lame, chickenshit way to avoid insulting
a person who can't decide what to call himself or herself.

Dan
5J

[youngbl...@gmail.com]

On Wednesday, April 12, 2023 at 4:13:14 PM UTC-4, Eric Greenwell wrote:
> Recently, Old Bob the Purist wrote:
>
> "Eric, you must admit that convenience and safety go together. What is interesting is the reliability of the motorglider when needed. I can only recall two instances where the motor did not start when called upon that resulted in land outs. Once was during a Seniors event when some guy left an airport area low and was going to rely on the motor and it did not start when called upon and the other there was a malfunction of the engine and it would not start and also resulted in a land out. So with that said I would like for you to give me some idea as to the percentage of reliability that you would put on a motorglider start when needed, I would say that the reliability is probably 98%, which certainly makes it a save your ass safety device. Old Bob, The Purist"
>
> A motor does not automatically give you safety or convenience. For some pilots, the additional complexity and cost of a motor exceeds the convenience of tows when desired, and for others, that complexity decreases their safety when low and under pressure to avoid a landout.
>
> But it's good question: just how reliably does a motorglider start? That's a bit like asking "how reliable is the L/D on your glider", because L/D is what most of us depend on to keep us safe during a flight. The answer to both questions is "it depends"; for example, the type of motorglider, it's maintenance, and pilot ability can all strongly affect the success of an attempted start in stressful conditions (and knowing you will crash if the engine doesn't start is definitely stressful). The older (before the DG400, say) two stroke motorgliders are, I think, worse than 98%, but the modern FES glider is much better than 98%, possibly enough better that many pilots would be safer depending it starting than the safety of a field they pick out from the air.
>
> Using your 98% reliability for starting, I'd expect to have a failed in-flight start about once every 10 years. A crash every 10 years sounds like very poor odds to me! No crashes for me, however, even though I made a lot use of the convenience of my motorglider to enhance my soaring experience, as I maintain my safety because I don't count on it starting to "save my ass". You, on the other hand, would gain neither convenience nor safety with a motorglider, unless you change the way you've been flying the last 5+ years.

Eric, I noticed that your flight of 4-19-23 was not accepted by OLC because of your logger, what happened, did it not pick up the starting of the motor to SYA? OBTP

[2G]

And I will stand by my assessment that you have no real data to back up that statement. Prove me wrong - I can take it.

Tom

[Eric Greenwell]

On Thursday, April 20, 2023 at 3:20:49 PM UTC-7, youngbl...@gmail.com wrote:
.
> Eric, I noticed that your flight of 4-19-23 was not accepted by OLC because of your logger, what happened, did it not pick up the starting of the motor to SYA? OBTP

I don't know what causes the "unverified" status. That's new this year. The logging itself seems correct, as it shows the launch, and the only relight this year (April 4). The OLC still scores the flight and places me in the correct position in the daily standings, so fixing it is not a priority.

[Eric Greenwell]

If rates really are higher (and I tend to agree with you, but I'm not sure it's true), then I would say "motorgliders are not safer". Higher operational complexity, additional maintenance requirements, change in pilots risk acceptance (eg, accepting poorer potential landing areas than when flying a towed glider), higher landing speed due to more weight, more exposure due to more flights - all tend increase the risk of operating a motorglider, perhaps mitigated to some extent by fewer field landings.

But I don't think we can compare towed glider rates to motorglider rates to decide about the safety of towed vs motored, because the pilots demographics are likely very different; also, where and when they fly might be significantly different.

Eric

On Wednesday, April 19, 2023 at 11:24:17 AM UTC-7, Dan Marotta wrote:

[Dan Marotta]

Kinda what I was alluding to with fewer words.

Now 2G Tom wants me to prove something that is not provable; that
experience (or training, if you prefer) makes one a safer pilot. That,
by extension makes the aircraft that he is flying "safer".

Example: I have flown jets, turboprops, piston powered airplanes,
gliders, and gyroplanes and pure gliders and never had an accident in
any of them. Does that mean that every aircraft I have flown is safer
than the motor gliders that have had accidents? The answer is clearly
"NO". It's the pilot's lack of training, experience, or momentary loss
of focus that causes the majority of accidents.

Maybe I can come up with a second order partial differential equation
that will satisfy Tom's fantasy...

Dan
5J

[2G]

Dan,

Let's review what you wrote:

"Well, you could look at accident RATES rather than NUMBERS. I would bet
the rates are higher for motor gliders but I'd also bet that the higher
numbers are due to higher complexity and, possibly, pilots who are not
always capable of handling the additional complexity."

Now, are you saying that these RATES are unprovable? Seriously? BTW, a "rate" IS a number, so what you wrote is a direct contradiction with itself. This is not that easy to do, but you did it.

Again, your use of the phrase "I will bet" is not "I have the evidence that PROVES." Second-order partial differential equations are an interesting topic, but not germane here. For further reading try this:
http://www.personal.psu.edu/sxt104/class/Math251/Notes-PDE%20pt1.pdf

Tom 2G

[Dan Marotta]

Not getting sucked into a pissing contest with you, Tom. Enjoy your
superior intellect.

Dan
5J

[youngbl...@gmail.com]

Dan, it is not called intellect, it is called arrogance, DSM5 is a legend in his own mind, even his fellow motorglider geeks know he is a nutcase. Look at some of his postings, it is obvious that he needs help. Old Bob, The Purist

[2G]

Well, Dan, you ALREADY engaged in a pissing contest with me, and it looks like you LOST!

Tom 2G