Stall speed

[Stan Campbell]

I just bought a Eagle II and have six hours in it now. My question is the specs say stall is 58 mph. My Eagle stalls at 80 mph and I come in 100 over the fence and touch down about 85. I've checked the speed with my GPS and both speeds are the same. I can't understand why it would stall at 80 and not 58?

[David Wolf]

Have you actually tried to hold straight and level flight, at 1 G, at 80 mph !!!  It should do this with no problem.  It is hard to believe it could be so out of rig so as to reach the stall angle of attack at 80 mph.  So much so that I would say you should not fly the airplane.  At greater than 1G, of course, one may reach the stall AOA at any speed if enough G is pulled.  That is how one snap rolls at, say, 110 mph.  We will be interested to understand the resolution of your problem.

 

Dave

[Kurt Haukohl]

I am interested too.  Hopefully you wont get upset if everyone badgers you.

 

To be fair, Stan, true you cannot actually land in a full stall at 58 MPH.  I never thought you might actually be able to do a full stall landing.  That's crazy because your nose might be 30-60 degrees high.  Your touchdown would be some kind of tail low, out of control, slam on to the runway.  My guess is your touchdown might be more like 80 MPH.

 

I think David is correct though, the definition of a stall, with a full break and session of flight should be more like 58 at zero thrust.  If your idle is set high and your putting out more thrust this stall speed could be near zero.  So we should consider your somehow creating more drag than designed.  Do you have a wood prop?   Can  you share your engine, propeller, and any special rigging set up with us?   I too was never comfortable with 90 MPH, more like 100-110 for me.  I do believe you need to have the proper angle of attack which is nose down, not some rapid nose high sink, or even a nose level high sink rate.  Focus on attitude, not airspeed.  You may guess my background is seaplane not so much taildragger.  You simply cannot put a seaplane on the water in an incorrect attitude, who cares what airspeed you have. 

 

I've pulled out the incidence and the angle of attach in my plane just a bit, and even my 'lead sled" stalls at about 58.  At full power it hovers for a while, about straight up.  Don't worry too much about what others publish as normal or typical.  If you need fast, just go fast.  My friends laugh at me and with me when I tell them I hit my highest speeds on final.  I do have a BIG wood M&T 200 wide cord prop, that is like throwing on the brakes.  I land fast but under control and stop about where everyone else does without brakes.  If your flying in Leadville or Denver go fast please. 

 

On the QT are you way over 200 lbs?

 

Kurt O. Haukohl
PO Box 1413
Manhattan Beach, California
90267-1413
Office:  (310) 725-6688
Mobile: (916) 825-3102
Home:  (424) 772-1512
.
Sent from Palos Verdes Peninsula, CA, United States

[CNC]

Mine does the same thing,,  --------  Dan   Roseburg Oregon.

---

From: christe...@googlegroups.com [mailto:christe...@googlegroups.com] On Behalf Of Stan Campbell

Sent: Monday, October 26, 2009 4:50 PM

To: Christe...@googlegroups.com
Subject: Christen-Eagle Stall speed

[FrancoisMarquis]

Here's a "may not be so crazy" idea. How about a leaking static port
tube somewhere. You know, at a Murphy-esque location that would cause
a much higher IAS deviation while on high AOA (as in "close to the
stall"). Leaving you with reasonably accurate values in normal flight
(as in my GPS reads pretty much the same).

Hint: are your altimeter readings the very same when your flare and
when you do come to a stop?

It is good to first prove that this is not an instrumentation related
issue.

Francois

> On Mon, Oct 26, 2009 at 7:15 PM, David Wolf <dwol...@wolfster2020.net>wrote:
>
>
>
> >  Have you actually tried to hold straight and level flight, at 1 G, at 80
> > mph !!!  It should do this with no problem.  It is hard to believe it could
> > be so out of rig so as to reach the stall angle of attack at 80 mph.  So
> > much so that I would say you should not fly the airplane.  At greater than
> > 1G, of course, one may reach the stall AOA at any speed if enough G is
> > pulled.  That is how one snap rolls at, say, 110 mph.  We will be interested
> > to understand the resolution of your problem.
>
> > Dave
>

> > *From:* christe...@googlegroups.com [mailto:
> > christe...@googlegroups.com] *On Behalf Of *Stan Campbell
> > *Sent:* Monday, October 26, 2009 6:50 PM
> > *To:* Christe...@googlegroups.com
> > *Subject:* Christen-Eagle Stall speed

[dwo...@wolfster2020.net]

Theoretically anyway, a leaking static port would not affect the "static
pressure" but a leaking ram air port would cause a falsely low airspeed
reading. The problem we are discussing sounds like a false high reading -
he reads a high speed when actually going slower, in this case as slow as
stall speed, but reading 80ish. Same with a blocked pitot tube. It's hard
to fail the system to read high. Especially if it cals out at some speed

Dave

[Jay Silcott]

I bought an Eagle a year ago and had a similar prob high speed indication and in flight altimeter error.
the fix recal ALT and leaking VSI.
 
Cheers,

Jay Silcott
Silcott Aviation
Sales & Solutions
 816-803-0056                              
Silcottaviation.com

[FrancoisMarquis]

Dave, maybe I was not very clear in my explanation. An airspeed
indicator shows the pressure differences between the pitot line and
the static line.

A false high reading is either an excess pressure in the pitot with
nominal static pressure, or alternatively a nominal reading on the
pitot and a low pressure induced in the static line. That low presure
(we could call vacuum) is what can be measured inside the cabin, or
inside the leading edge of the wing.

A simple proof of that is to activate an alternate static in a non-
presurized aircraft, you will loose a good 500 feet of altitude and
gain 10 knots of IAS. At least that is what I observe in my Lancair.

I thought that the situation explained in that thread was related to
that condition.

Francois

[David Wolf]

So, to follow on our logic in pursuit of our common understanding of this
matter;

If you opened the static to in cabin pressure, and it read a lower altitude,
then the in cabin pressure must be higher than the ambient external
pressure. Maybe a Lance Air will hold pressure but an Eagle should be well
equalized. In your case, the difference between ram air pressure and static
pressure should be reduced (static pressure went up (lower altitude
indication) and ram stayed the same). So it should read a lower indicated
airspeed !!! But you saw a higher indicated airspeed !!! So, somewhere my
logic is wrong or I am not understanding the facts correctly.

I enjoy our detective work in ironing this out until we all understand it,
and correcting my model of the world as it would be in error.

Thanks,

[Ron Renz]

What entry rate are you using for the stall speed measurement?  You need to decelerate slowly.  The FAA definition  of stall speed is a deceleration of 1 Knot per second.  That is pretty slow.

 

I am betting that your stall speed measured at 80 is with a much higher entry rate,  or check the below items.

 

Have you checked your Pitot and static system for leaks.  If there are leaks all bets are off as to what the speed (and for that matter altitude) really are.

 

Have you checked that your pitot tube is straight and not bent?

 

How about blockage, (insects, water, dirt, etc.)  disconnect the lines in the cockpit near the wing root,  and blow it out with air to make sure (make absolutely sure that there is nothing connected (No instruments,  transducers,  encoders connected to the lines you are blowing out,  because you will destroy them if there are.)

 

Just some things to try.

 

 

   ___

   o|o

---( )---

 

Ron Renz

No Plane - No Gain!

Business Aviation is a tool that helps drive American businesses forward,spread the word ... www.noplanenogain.org

 

GUT Works, LLC

(785) 312-9880 (office 1)

(785) 749-0900 (office 2)

(785) 749-0988 (fax)

re...@gut-works.com (email)

www.gut-works.com

 

 

 

From: christe...@googlegroups.com [mailto:christe...@googlegroups.com] On Behalf Of Kurt Haukohl
Sent: Tuesday, October 27, 2009 12:30 AM
To: David Wolf
Cc: Stan Campbell; Christe...@googlegroups.com
Subject: Christen-Eagle Re: Stall speed

 

I am interested too.  Hopefully you wont get upset if everyone badgers you.

<br

[FrancoisMarquis]

Gee, I was writing without reading. The altimeter indeed will and
does show higher. I recall a situation whereby engaging alternate
static while the autopilot was on altitude hold and the memorable
plunge that resulted it... so I was thinking "down" whereby the
actual indication is up. So please don't change your model of the
world on a semantic error on my part. ;0)

Not that my Lancair is particularely airtight, but airflow dynamics
are such that a lot of pressure differential exists even in our
Eagles. Two years ago I broke my Eagle canopy inflight and the crack
opened a good inch on the reduced speed flight back to the airport...
Upon landing the two parts mated again ...

Anyhow, to put a nail on this idea, my logic is simply that a leak on
the static line in an area that has a negative pressure with respect
to ambient (pure static) air will result in a higher IAS reading.
Given that at different AOA we have quite different air pressure
distribution patterns, this may also explain other aspects of the
situation (e.g. it cals at a given airspeed).

Short of having a comprehensive pitot/static test made by Stan, this
entire situation is very much instrumentation error prone IMHO.

Cheers!

Francois

[Ben Lovering]

Could you fly alongside someone and compare airspeed readings?

[André van Rensburg]

Hi Stan

I believe that you may just have an inaccurate airspeed indicator
(instrument error). I suggest you have it tested by an Instrument
Technician.

You cannot compare your GPS readings to your IAS because a GPS
measures ground speed, which has a TAS and wind component. You may get
reasonable result on a windless day by converting the GPS reading
(TAS) to IAS.

For a given configuration an aircraft will always stall at the same
angle of attack (AoA) irrespective of the airspeed. If you were to
execute a 1G stall (with an accurate airspeed indicator) the aircraft
would stall at 58mph, but if you were to do the same during a 60
degree turn the stall would occur at a higher IAS. Interestingly
enough the stick position is a very good indication of the angle of
attack and would have the same stick position (AoA) in both cases.

With increased power an aircraft will stall at a lower IAS because the
relative airflow over the wing is reduced by the slipstream of the
propeller, but once again, it will stall at the same angle of attack.

Happy landings
André

[G. Ertl]

Hi Stan,

Maybe I can add something to the discussion. As someone pointed out
before, the stall speed is measured by slowing the Airplane one Knot
per second. A stall is occurring (According to FAR23) when one of
three things happens: 1) An uncontrollable nose down movement (nose
drops even if you pull more), 2) The control reaches the stop (It’s
not possible to slow the aircraft further), 3) The stick pusher fires
(Since the eagle is no Airliner it does not have a stick pusher). A
Stall in the eagle shows uncontrollable nose down movement. So when
the buffeting starts and the stick is shaking, this is by definition
no stall. When an airplane is loaded correctly (nose heavy) the
elevator is pushing down and the Wings are pushing up. The Stall
normally happens because the airflow on the elevator is not clean
enough to keep the nose up. So on a normal airplane the aerodynamic
stall happens on the elevator, not the wing.

This is very important for safety because when you fly an airplane
with a very rear center of gravity you have to push the stick to keep
the nose up. When you slow down you have to push more to keep the nose
down. Sooner or later you can push no more and the tail goes down and
the nose goes up, slowing the airplane even further. By then you are
in an unrecoverable stall and there is no way to get the airplane to a
normal attitude again. Since this should not be possible, nearly all
airplanes are constructed, to recover a stall by themselves. They are
a little nose heavy and when the elevator can no longer produce enough
lift to push the tail down, the nose goes down and the airplane
accelerates.

The eagle and most other aerobatic planes have a center of gravity
very far rear, but are still nose heavy, just not as much as other
planes. So the elevator does not have to push down as much as in a
cesna. Also does the eagle have a more effective elevator than normal
planes. So it is possible to stall the wing in the eagle even in a non
accelerated stall. But to do this without power you have to pull very
smooth. If you pull to fast the elevator will stall before the wing
reaches the critical angle of attack. It much easier to do with power
since the engine produces a lot of airflow on the elevator. I have not
checked, but i think i could fly the eagle straight and level well
below the power off stall speed. It works at 70 MPH, but i think it
could go much slower.

To make it short: On my eagle the first buffeting starts at around 80
MPH. But the actual stall happens much slower.

You wrote that your touchdown speed is around 80 or 85. I touch down
at the same speed in three point attitude. So i would assume that
everything is correct with your eagle and your indicated airspeed is
ok.

greetings Gerhard

> > Could you fly alongside someone and compare airspeed readings?- Zitierten Text ausblenden -
>
> - Zitierten Text anzeigen -

[Eagle N23TS]

A different perspective here...

Maybe all would agree to some degree.

If you have 6 hours in a Eagle and are still working on your landing
trchnique, you are just like the rest of us. If you have 100 hours or
more, you get to the point that the airspeed is a reference
instrument. The primary reference is the attitude, sight picture and
feel of the stick. That may read crazy, but I think all of us are
there or getting there in regard to approach to landing and touchdown.

The good news is you are 100 mph over the fence and try 110 if gusty.
I approach at 100 to 150 depending on the day and aggressive pattern.
I touch down at 70 to 80 (three point/wheel landing) solo. With two
people, the touch down speed is increased 5-10 mph and a wheel landing
is very difficult if not impossible (for me). No doubt there were a
few that tried the 70 mph approach expecting a 60 mph touchdown and
learned the hard way if they or the aircraft survived the mistake
without a serious hard landing. In my Eagle the elevator looses most
of its effect at 80. I make very steep approaches so I have a lot of
downward vector to stop. I land on the numbers or just beyond each
time.

I can land and have done so Dead Stick on about 30 occasions. DONT
TRY dead stick until you are well insured and have a remarkable sense
of the Eagle and its feel. I did it for no other reason than
stupidity and I fly a lot of gliders. I have had two real world
engine/prop failures so my reasons are important to me and stupid to
others. Not trying to start the debate... Just pointing out I have a
wider range of landing than most and wanted to emphisze your doing the
right thing by asking on line.

I've been through the numbers and trouble shooting you currently seek
and were/are reccomended in this thread. You may have noticed non of
the replies have contributed to the answer you seek, just point you to
more questions. You sound like your head is in the right place and
you are flying safe.

After about 1000 plus landings you will simply have a feel for the
Eagle and understand that traditional "flying by the numbers" kind of
training does not really apply. There is a reason Pitts and Eagle
scare 90% of the pilots out there. These planes have a personality
and are not easy to fly, hence the low numbers (approx 100 flying) of
Eagles on the globe.

You are in rare company and quite exclusive to own and fly one.

Maybe consider throwing away the checklist, FAR, the eagle manual, and
look out the canopy. Learn the angles and feel the stick. Reference
the airspeed and altimiter as a suggestion or trend. The Eagle is a
true 3D machine. The speeds dont mean much as a picture as seen
throught the canopy. You should be able to cover them all up and fly
just as well. If you cant, you will truely miss the pointof owning
the Eagle and the real pleasure of owning one. This applies to every
maneuver by the way. There is a reason we put string on the sighting
device, there is a reason the cabane strut is a upside down V. They
are made to look at. Have you ever wondered why the altimiter and
airspeed instruments are 4 feet out of reach and hard to see?

> > - Zitierten Text anzeigen -- Hide quoted text -
>
> - Show quoted text -