EAAAirVenture OshkoshShopJoin

Take off and landing flight testing suggesting

Posted By:
Paul Hutson
2
Posts
0
#1 Posted: 6/9/2011 00:06:23

Perhaps I have missed it here (SEARCH doesn't find it), but do members and/or chapters have suggestions for publications or procedures by which we can establish a take-off and landing table for our homebuilt (or certificated) aircraft?  I would think that in lieu of moving to low and elevated fields one could run tests on really cold and hot days to get some sense of the effect of density altitude.  What suggestions and experience do you have for measuring the distance for landing and take-off, and making it over the 50ft tree both ways?  Other suggestions?  Maybe regional chapters could organize testing fly-ins that might charge for the use of rangefinders or something that could be rented from the EAA mothership?  Seems more accurate (and safer) than posting observers along the runway like a javelin toss competition.

Thanks in advance.

Paul Hutson

Glastar N97BM



Eric Witherspoon
Homebuilder or Craftsman
29
Posts
3
#2 Posted: 6/16/2011 16:00:37

You may have seen the thread on aviation quotes.

The one that comes to mind here is, "if the runway looks too short, it probably is."

I have a copy of "Flight Testing of Homebuilt Aircraft" by Vaughan Askue.  It's been a while since I looked in there, but if I can find it, I'll see what he has to say.

Keep in mind that even if you have data, the day you try to use it, the "tree" won't be 50 feet tall, you won't know _exactly_ how far away it is, the wind won't be the same direction or speed, your airplane will be older / have more time on it, and thus have any number of reasons it's not making the same power, you won't know exactly what weight it's loaded to, as it collects "stuff" over the years....  So I refer back to the quote.

Best bet if you're not feeling comfortable is to offload some cargo, passengers, and fuel, wait until the cool of morning or the wind comes back around, and go down there and cut down that tree or see if a little side-shift / turn might make getting out easier...

 



Andy Gamache
Homebuilder or Craftsman
122
Posts
28
#3 Posted: 6/19/2011 09:20:24

If you can find it, Understanding Performance Flight Testing: Kitplanes and Production Aircraft by Hubert Smith takes up where Askue's book leaves off. Unfortunately, it appears that it's out of print and is currently being sold at a scalping premium price. BTW... Askue's book is great with taxi tests, envelope expansion and flight characteristics, but barely mentions anything about performance testing. Smith has a chapter on the initial testing, but gets into a lot of detail on performance testing.


http://www.amazon.com/Understanding-Performance-Flight-Testing-Production/dp/0071376798/ref=sr_1_2?ie=UTF8&qid=1308492217&sr=8-2


Essentially, you do the tests on a calm wind day, record the temp, altimeter and field elevation. The book gives you formulas that you can plug into a spreadsheet that will convert for different density altitudes and weights.


Doing the tests will be much easier with a video camera pointed towards the wing. The airfield I did this at had runway lights that were each 200 feet apart. I videoed the takeoff and landings (three in each configuration for averaging) and used that to come up with my figures. When figuring out the distances needed for the formulas, I watched the video and used the runway lights as a measurement for distance.


For the takeoff, you're essentially measuring your acceleration (how long it takes to pass each runway light). However long it takes to accelerate to your takeoff speed will determine how much distance you need. Landing is similar, but you're only measuring the distance from touchdown to full stop.


BTW... Due to the requirement to generate polynomial equations from the numbers you generate, Excel is probably the best spreadsheet to use.



Ron Blum
Young Eagles Pilot or VolunteerHomebuilder or CraftsmanAirVenture Volunteer
13
Posts
2
#4 Posted: 6/22/2011 09:33:32

Paul:  All of the suggestions above are good.  Is there any way for you to use your GPS (or 2 units and make Differential GPS (DGPS)) measurements?  The biggest item that is often missed or ignored is to calibrate the airspeed system.  If you're looking for what the OEMs do, the regulations (14CFR23 ... commonly known as FAR 23) and the related Advisory Circular (AC23-8B) are both online on the FAA website (just Google it).  These will definitely get you started.  -Ron



Sonja Englert
Homebuilder or Craftsman
18
Posts
1
#5 Posted: 6/22/2011 12:23:51

There is one book specifically for flight testing homebuilts, and it has a lot of advice how to do this with simple means. Performance testing is also covered. Check out http://www.caro-engineering.com for the book "Homebuilts Aerodynamics and Flight Testing"

 



Andy Gamache
Homebuilder or Craftsman
122
Posts
28
#6 Posted: 6/23/2011 00:00:33
Sonja Englert wrote:

 

There is one book specifically for flight testing homebuilts, and it has a lot of advice how to do this with simple means. Performance testing is also covered. Check out http://www.caro-engineering.com for the book "Homebuilts Aerodynamics and Flight Testing"

 

 

Sonja,


First time I heard of this book. When I was doing my final masters project, I was looking for all kinds of flight testing resources. I'm surprise I missed this.

Looks like it came out roughly the same time as Smith's book I mentioned above. I'm curious if you've ever had a chance to compare the two.