HM order

[Becky Green]

Just a reminder that I'm going to be doing a bulk buy from Hawk Mountain.  Please email me off list at apfu...@yahoo.com with your requests.  I'd like to place the order by end of October if possible so I can get everything before the holiday season. Thanks, Beck

[Thomas Kernes]

I think that I’m good.  Thanks.

on 10/14/10 7:52 PM, apfu...@yahoo.com wrote:

[Jamie]

Got mine today and in review of its configurations one thing I didn’t know it can do is trigger the second event  at Apogee - 150’.

This actually sounds better than a timer delay because if it’s descending  it should be oriented the right way, no?

What are do others think of using this instead of the timed delay?

[Jordan Raice]

Seems like a great option to me. Can't think of any cons.

[Ken Biba]

Two.

It is Adept.

Wrong delay for ARLISS flights.

K

[Jamie]

I know – but that’s why I wanted to pose this question to the group.

 

With a timer, even 7 seconds – you can’t be certain to be descending.  

[Jamie]

What do you mean by wrong delay? 150' drop?

I've heard people complain about Adept, but I've flown their stuff before
without problems.

-----Original Message-----
From: arliss...@googlegroups.com [mailto:arliss...@googlegroups.com]
On Behalf Of Ken Biba
Sent: Saturday, March 05, 2011 4:07 PM
To: arliss...@googlegroups.com
Subject: Re: [ARLISS Flyers] ADEPT 22 Avionics

[Ken Biba]

The standard ARLISS delay if 4-6 seconds .. not 150'.

Having studied the technology of baro sensors extensively, Adept either lies on their accuracy or is incompetent. I would STRONGLY prefer we not approve their products for use on ARLISS. I know many have had success with their products for simple recovery - however ... their analysis of accuracy on their products is so blatantly wrong it offends all my training as a scientist.

Tommy claims a few feet of accuracy of altitude ... simply impossible since the conversion of pressure to altitude is based on an atmosphere model that simply has 5% average error baked into it even with perfect pressure accuracy - at that is not achievable either. 5% error at 15k' MSL is about 800'. MUCH higher than the 150' alleged altitude drop for the second event.

I can go at quite some length on this discussion ... without much amusement ..

K

[Jamie]

FWIW - same Altimeter has an option to set it to 6 seconds after main.

Actually more than the brand of altimeter I was curious as to what people
thought about the idea of Apogee - 150' as the trigger point.

So you're basically saying that barometric altimeters aren't accurate enough
for the second event based on drop and will likely fall much further, right?

That seems like a valid concern for sure.

[Ken Biba]

I have a particular concern for Apogee products since their specs are manifestly false.

I have more general concern about baro measurement accuracy when expressed in feet. Simply a problem of physics.

The standard has always been apogee - 6 seconds ... and I think we should stay with that.

K

[Ken Biba]

Actually .. let me add to this rant.

I believe Adept makes reliable products to detect apogee and deploy - particularly for subsonic flights.

I have STRONG reservations on their alleged accuracy and call bullshit on that.

I am not personally convinced about the magic of baro filtering for transonic flights and would not personally use their products on transonic flights.

If used on a subsonic flight, with a second event a given number of seconds past an apogee event .. I am fine with that use of an Adept product.

K

[Jordan Raice]

And what makes an acceleromic device for accurate for altitude detection? A rocket can launch at a skew angle and say it went significantly higher than reality if you rely on acceleration data.

Sent from my iPhone

[Ken Biba]

Oh my....

Depends on what we are measuring. Sadly, no one sensor is good for everything.

Accelerometers do a VERY poor job of reporting altitude ... as you correctly point out ... they depend on a vertical flight which almost never happens. HOWEVER - they ARE very good at detecting the zero vertical velocity apogee event and the deployment sensor of choice for transonic flights.

Baro sensors are not bad at detecting apogee (but only about 2-5% accurate on the actual altitude), necessary for detecting the main event on two phase deployment .. and for us old guys .. some residual suspicion about susceptibility to the baro pressure spike during the transonic transition that could trigger a deployment event at MaxQ. Old Adepts were famous for this - triggering the apogee deployment charge at about 700' AGL - perfect for destroying airframes and cert flights.

For accurately reporting altitude .. the right GPS is the sensor of choice but not particularly useful for deployment.

So ... what do I use?

I rely on avionics with a good accelerometer based apogee detection event for drogue deployment (my personal choice is the Featherweight Raven) and a good baro sensor of two phase main deployment (my personal choice is the again Raven). In large projects, I use the RDAS as backup to for both. For subsonic (low and slow) flights - a baro sensor can work well for Apogee deployment. Lots of good products here ... Adept is fine, I personally prefer PerfectFlite. Not for accurate altitude reporting, but for reliably triggering recovery.

For accurate altitude determination - I use the Beeline GPS .. though GPSFlight is also good.

K

[Jamie]

Aren't the ARLISS 6"s all subsonic? Thought they were.

[Jordan Raice]

Either way timers integrated into the alt can be used to prevent ejection during the transonic part of flight.

Sent from my iPhone

[Jonathan DuBose]

Ken,   So are you giving the ADEPT22 your blessing to use on ARLISS since the flights are subsonic?   I will add my 2 cents worth on ADEPT:  I have flown the ADEPT "ALTS2 50K" as a "backup" every on mach+ flight I have ever flown..which is probably not more than 10 flights.  I have also flown it solo in flights that were probably mach. All these flights were nominal except the sustainer I augured in at MUDROCK 2009 but the main computer was an ARTS2 and both apogee charges fired.  So if ADEPT has a problem with mach flights it doesn't appear to me to be a detrimental issue. Most recently I flew the ALTS2 along with an HCX in my Mongoose75 at XPRS...mach 1.4.  Perfect recovery.    Although I don't normally archive the flight data I remember the ADEPT baro reading being about 800ft higher than the HCX baro reading which might correlate to the error that you mention (assuming the HCX is in the ballpark at 21262').                                     --- On Sat, 3/5/11, Ken Biba <ken...@gmail.com> wrote: