Power off decent rates 7 vs. 9 vs. 10

[jantar]

I recently talked to a guy who lost a friend in an RV-8. The RV-8 pancaked to the ground because the pilot failed to maintain air speed and the decent rate was too great. He did not have much kinetic energy when time came to rotate. As I was listening him talking I started asking myself a question; how fast RVs are going down once the power is off. I have heard about RV-9 500 fpm on idle engine. Is this a correct number and what about RV-7 or RV-10? I would like to hear from people who performed simulated landings in power off configuration say from 2,000 feet. What is your experience? What is the decent rate, what was your experiance when it came to rotate?

[rv6ejguy]

I've actually forced landed a 6A dead stick. Descent rate was around 900-1000 fpm at 80-85 knots. A 7 should descend a bit slower due to the extra wing area and a 10 maybe about the same as the 7 because of the extra aspect ratio.

Dead stick descent rates are noticeably higher than at idle power. The residual thrust from 8-12 hp makes quite a difference when you figure an RV only needs around 30 hp to maintain level flight.

The big thing that people don't anticipate is the rate at which the ground rushes up at you in the last 100 feet and the very strong urge to arrest the descent rate by pulling back. This of course increases the descent rate and the impact forces. Best glide speed needs to be maintained down to about 10 feet before the flare is initiated no matter how scary the attitude looks. Elevator authority/ response dead stick is also noticeably slower.

The low aspect ratio wing on the 3-8 models also has considerable induced drag at low speeds so beware/ avoid any banked turns over 30 degrees below 500 feet as this increases the nose down attitude required to maintain airspeed and descent rate, fortifying the urge to pull back. I found myself having to push forward to maintain airspeed as the ground rushed up. This is counter intuitive to self preservation!

[Bryan Wood]

Not really on topic, but yesterday I flew a friends V-Tail Beech. This was my first time flying a Bonanza and what really got my attention was the sink rate when landing. I've got around 340 hours of flying the 9A with time in nothing else since getting it flying so the wonderful flying qualities are just what an airplane is supposed to feel like to me now. Yesterday as I was on short final and coming over the fence he said "Now chop power" because the field was made. In his words "The Bonanza sinks like a flying refridgerator once you cut the power." He certainly didn't exagerate at all and the rapid pancaking towards the runway caught me totally off guard. This resulted in flaring to much to soon and a ballooning, and finally a nice firm landing. I can't imagine any RV with a failed engine coming down faster than this! As for the Bonanza overall, well I kinda liked it!

Regards,

[David-aviator]

To echo what RV6ejguy said, I too have made an engine out landing with the 7A. The engine quit at 1000' agl and I was on the ground in about one minute. There wasn't time to do much trouble shooting, only fly the airplane. That's the challenge. Fly the airplane.

Instinctively, we want to sit there and determine what caused what to happen and fix it. But my eyes saw the airspeed dropping to 80 knots and the brain kicked in and said fly this SOB. A quick scan to the left picked out a dirt road between a couple fields and a 270 turn was made to that spot. Flaps did not come out until short final and speed was set at 80 to 90 knots the whole way. The thing came down quick and this was with the prop stopped - probably 1000-1200 fpm. You have to keep the speed up no matter what the descent rate so as to go into the flare with plenty of energy. As Bob Hoover says, fly the airplane as far as possible into the crash.

It is impossible to say one airplane will descend better than another. There are too many variables. The 9 with fixed pitch probably is the winner due to its larger wing but GW, CS prop not feathered can have a very significant impact on how far a machine will glide. As a pilot all this does not matter a whole lot. You have no choice but to fly the airplane as long as possible and hope for the best. Do not under any circumstances level off at 500' because you don't like the trees or rocks in front of you.

dd

[Kevin Horton]

The prop makes a huge difference. A constant speed prop goes to full fine pitch once the rpm is less than the selected rpm, and this is a much finer pitch than on any fixed pitch prop. So, even for the same type of aircraft, there are many variables:

idle vs engine failed,
fixed pitch vs constant speed prop,
airspeed, and
flap position.

Weight is a minor variable. Wind shears on short final can have a major impact.

[jantar]

Kevin not every prop goes to a fine pitch after loss of power. I flew behind props that go into coarse pitch on engine failure and this includes small planes. There are many solutions pressure to fine or pressure to coarse or counter weights.

[Kevin Horton]

Originally Posted by jantar

Kevin not every prop goes to a fine pitch after loss of power. I flew behind props that go into coarse pitch on engine failure and this includes small planes. There are many solutions pressure to fine or pressure to coarse or counter weights.

Props on multi-engine aircraft, and aircraft designed for serious aerobatics are generally set up to go to coarse pitch if oil pressure is lost. I doubt many RVs have props like this though, as the props sold by Van's are set up to go to fine pitch if oil pressure is lost, as far as I can tell.

[DanH]

I try to fly every approach a bit high and chop to idle for a steep short final, as I believe folks who grind in long and flat often die when they develop a power problem.

The descent angle is not as steep as with higher drag aircraft. Plenty of flare time/energy flying short final at 80 mph in an RV-8A at forward CG, power at idle with a constant speed prop. It can be done slower.

I guess it all depends on what you're used to. I once had a WW1 replica with a deadstick "landing cone" inside the inboard edge of the ailerons.

Dan

[Walt]

I agree with the above, I chop power abeam the numbers at 1000 - 1500' and if I need to add power to hit the chosen td zone then I blew it. Should a power off landing ever be required I think I'll be ready.

[gmcjetpilot]

Touch down at best glide or min sink you get you hurt. The old adage, fly the plane first comes to mind. If you don't maintain flying speed and get to slow (stall or high sink) you've blown your survivability in any airplane.

With that said, the stall speed of RV's is incredibly slow, around 50 mph, which is the same as a C-150 or C-152, arguably one of the most docile trainers around.

A controlled crash at 50 mph is very survivable regardless of power off glide sink rate, but you have to lower the nose and FLY the plane to a touch down under control. The reason I first choose RV's in the mid late 80's was the safety aspect of the low stall speed and aluminum structure which yields and absorbs energy in an accident.

The pilot is key to the equation. If you stall or "mush" high above the ground and don't correct or don't have the altitude to affect a recovery, it does not matter what you are flying. Practice power off landings in the pattern is good advice. Even more telling is go from full power Vx or Vy climb and chop the power and go right to a nose low best glide attitude. It's a large pitch change. This simulates what it is like to loose power in the initial climb low to the ground. Basically it is a power on stall recovery. Key is to loose min altitude and maintain your energy (airspeed).

Consider power loss on take off with the nose way up. If you don't immediately lower the nose below the horizon about as much as it was above the horizon before the loss of power you may get into this stall/mush condition like the posters friend experience. Mentally you have to be ready to point the nose at the ground and land immediately, regardless of where that may be.

The topic of "180 degree turn returns" (really a 270 degree turn) and landing on the runway you just departed is a subject of much debate. My rule is no rule. It depends on the runway length, winds and surrounding off field landing options. I am not saying a return to the runway is bad or impossible, but have you practiced that? Chance's are you will be in a high bank angle low to the ground, with a higher chance of stalling. Those pilots who claim to practice the 180-return, say they can pull the power at say 400 feet can do it. Than they describe how they whip their plane immediately into a 90 degree bank, landing in the opposite direction on the same 6,000 foot calm wind runway they just departed. Good for them. The bad news is a real engine failure is always surprise. Runways and winds vary. Chances are for 1 to 3 seconds you'll be just sitting there, with your mouth open, (aircraft) nose in the air and airspeed bleeding off.

All I can say is an engine failure right after takeoff is a serious and horrible scenario. I hope you or I never have to prove our airmanship skill surviving this. When in doubt (as most are taught), fly the plane basiclly straight ahead or say 20-30 degrees either side and touch down under control wings level with full flaps at min speed. It does not take super pilot skills and currency. Of course if you are at 1000 feet agl and in the x-wind turn, sure you have more options; Again, have you practiced it lately. I know I have not.

At MIN before every take off mentally tell yourself or out loud say "In case of an engine failure I'm going to do XYZ". At least you will mentally have rehearsed it. Every commercial airline crew must review the engine failure reject or go scenario's before takeoff. It's a good idea even for GA pilots. It may not be as involved with a single engine plane, but know what you are going to do and do it.

My primary flight instructor who was a little sadistic gave me daily simulated engine failures from all flight conditions, sometimes several in one session. It was routine and felt cheated when I did not get a simulated engine failure. I am kidding, he was not sadistic, and later as a CFI, I did the same thing because sim. eng. fail from all flight conditions is FAR requirement for student pilots pre-solo training. Must admit I am rusty and need to practice. At least I know I am rusty.