Gear Retraction on Take Off

[aldoradave]

Originally Posted by Roger

If the self test is going to start at 10,000' at near gross, with the rear out, and doors open I believe we may have to wait a few days for him to get to 10,500'

Dear Roger,

Please note that N84E is a P337 and should have no problem getting from 10,000 msl to 10,500 with rear engine out. If it does I have bought the wrong airplane. My guess is that with the gear door mod it will be easier with the gear retracted.

Dave Dillehay

[RAY TORRES]

Hi Guys:

Normally I stay away from commenting here, but since the topic is my gear door mod I figured its time to clarify somnme things.

With regards to the RTAero gear door STC. The STC does not provide any procedural changes as to when to raise the gear or any changes in rates of climb/performance for before/after mod.

When we did this STC there was no doubt in our minds that the majority of the gear drag came from the large clamshell doors, and I think the modification has proved that out. I don't feel the wobbling or drag that I use to when cycling the gear before the mod. In addition, the modification removed 2 actuators and 4 hydraulic lines with no change in cruise or cabin noise.

As with most STCs, the FAA only requires that we show that the modified aircraft meets a minimum performance standard. In other words, you could modify the aircraft, and get approval for an STC where the aircraft performs worse or has no change from before being modified.

The FAA requirements to show improved performance figures is extremely cost prohibitive, thats why you won't find performance figure changes for most of your stol kits or other performance enhancing modifications. Normally you'll just get a general statement that the modification "improves" slow flight, rates of climb etc. The other side to this is the liability implications for the modifier when someone tries to fly to new performance figures and eats the trees at the end of the runway. Try to get hard numbers for any of the STC's out there and see what you get.

Getting back to the gear door mod. We did have to demonstrate to the FAA that the modified aircraft had positive rates of climb at 5000 feet and gross weight. We did a series of flights with front/rear and both engines in varying directions and averaged the results, and if my memory serves me right we averaged to around 100 fpm on the rear and about 60 on the front. But that was with an old tired airplane, performance will also be different depending on airframe and engine condition.

When you raise the gear is basically up to you. I raise my gear when I have positive rate and can't make the end of the runway. I do it even sooner if I'm taking off over water. But everyone is different and has to determine what is best for them. The "What ifs" are way too many to say one procedure is better than the other.

By the way, I blew a hydraulic hose the other day and had to sweat getting the gear down, luckily I had enough fluid to get it down and locked. But now I'm thinking that maybe the best solution is to just leave the gear down.

Best regards to all and thanks for supporting our mods.

Ray Torres

[aldoradave]

Dear Ray,

Thanks for stepping in. I own a scuba diving company in Cozumel and frequently look into associated web sites and threads--with the firm conviction that it is not my place to be posting. But sometimes I do and thank goodness you do as well.

Your post is much appreciated by me and most likely others. It was not possible for me to fly yesterday but I still intend to on Friday. MY plot is to take my P337 to 10,000 msl and try both engines out(zero thrust) one at a time of course, with gear down and then note rate of climb both before, during, and then after gear retraction. I do have your gear door mod, as well as Horton STOL.

The reason I pick 10,000 ft msl is that I frequently fly out of Mammoth Lakes CA and routine 10,000 ft density altitudes. So I really want to know what to do when the poop hits the prop!

If you or anyone else could give me a procedure that may be better than what I have in mind--that would be of benefit to everyone.

Thanks


Dave Dillehay