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crashworthiness, pants, trim

R

rphfly

I'm New Here
Hi folks-Just joined. Am in middle stages of planning to build an RV-9.

Do any of you have comments on the following questions, please?:

Thoughts on crashworthiness of RV's in general, and RV-9 in particular?

Is there such a thing as mechanical 3-axis trim?

Anybody fly RV's without wheelpants? Pros and cons.

Thanks, Ron
 
Ron,

Welcome to the VAF forum!

The crashworthiness of the -9 probably matches that of the -6 & -7 as they are very similar.

A good bit of the crashworthiness has to do with how you configure your panel, glairshield, harness (Hint, include the sub-straps), etc.

In the end, it is an experimental aircraft and does not have to meet the standards of a certified aircraft. I have heard but have not confirmed that the SbS RV's are very close to being able to be certified due to the seat ribs.

The key here is to simply not crash.
 
crash planning

Welcome Ron,
I'd advise sitting in someone's RV, and take photos and notes of where you want to reduce sharp edges etc. to enhance crash SURVIVABILITY.
Imagine your belts aren't perfectly tight, and the impact is not perfectly square on the nose, and look at what you are going to smack your face, legs, arms, head etc. into, especially if it flips inverted.
There are very few cockpits out there where these issues have been dealt with well, so a better example is the average late model car.
If I hadn't bought a finished plane, I'd sure consider some changes, and perhaps buying air-bag harnesses, would be high on the list.
also, consider the 100 lb of stuff behind you that will try to pummel, and / or decapitate you in a crash. I think we could do better in cargo area tie-downs and retention.
Testing has shown that the body can survive something like 23 g for an instant. We should all think about that when tempted to mount little plastic rings to hold elastic bungees over our tool-box in the baggage area.! :)
 
Pants

The answer to your question about flying without the wheel pants, most of us do that at some time. Mostly to create drag to help break the engine in.

This also means you have to remove the gear leg fairings. Expect about 15 mph/knot speed penalty.
 
Stall speed can play a factor here.

Van's has some interesting statistics in his preview plans regarding the survivability of a crash at 50 kts vs. 70kts. The difference is huge. I can't remember the numbers exactly so I won't quote them. What I can say is you are far more likely to survive a crash in a airplane with a slower stall speed than one with a higher stall speed. This of course assumes that you are flying the plane all the way into a crash. If you nose in, cartwheel, have a head-on collision I don't think it matters what you are flying then, the odds aren't good. Cockpit design, I agree, is the biggest factor outside of flying the plane all the way into the crash. The airbag seatbelts, while expensive, are a much better investment than any fancy toy you could put in your panel IMHO.
 
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Surviving the Impact

What Aaron says is correct. Remember, energy changes as the square of speed. The RV9 stalls at about 43 kts with flaps and 51 clean. If you haven't flown one yet, you need to make that happen. Try stalling it. Pull power, hold the stick full aft, and steer with your feet. The airplane behaves like a canard. It would be very difficult to hurt yourself unless you impacted a tree or a building on the way to the ground. Best of all, the 9 has a glide ratio of about 12:1. If you're at 5000 AGL and the engine quits, that leaves you with over 300 square miles of real estate to look for a landing site, and you really need less than 500 feet .
Regarding rudder trim, you really don't need it. The ailerons on the RVs, unlike Cessnas for example, are designed to offset adverse yaw. Very little input is required. At the same time, the rudder area on a 9 is pretty substantial, making the plane very easy to handle in stiff cross winds. Also, the longer wingspan of the 9 results in a slower roll rate and makes the plane a very capable and stable cross country machine. Ask the guys at Vans.
As for fairings, not really sure why you'd want to fly without them. The gear leg and wheel fairings contribute over 10kts to cruise speed, with the greater part of that coming from the leg covers. Here in Michigan, I've never bothered to remove my fairings in the winter, and have not encountered any problems. Just make sure that the clearances between wheel fairing and tire is sufficient. Good luck.
Terry, CFI
RV-9A N323TP
 
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