Pilot_DAR wrote:
There’s an important nuance between “hold the nose light” and “let it fly itself off”
Indeed. The procedure for the Alpha Trainer is to lift the nose wheel off (an inch or two) before 25 knots, then let the airplane fly itself off. Landing is the opposite. Land on main wheels, put the nose wheel (gently) down when passing 25 knots.
I wonder about that rotate. For airplanes with CG well FWD of the main wheels, I guess it makes sense? What is the common reason?
Vrot: Used instead of VR (in discussions of the takeoff performance of military aircraft) to denote rotation speed in conjunction with the term Vref (refusal speed).
My simple explanation: As used on the airliner, Vrot is between V1 and V2 and denotes the action for the PF to pull on the pitch control to permit the heavier than air to leave the surely bound of planet Earth 
A word (or two) about the word “Rotate.” This word was first used after we began flying swept-wing jet transports, and is a highly-defined term of certification which covers the technique of accelerating down the runway in a minimum-drag attitude to V1 (go/no go speed), Vr (rotate), with a precisely timed change in deck angle, which places the aircraft at a speed above Vmu (Unstick), and in an attitude which produces V2 at an altitude of 35 feet with an engine out, OR V2+10 with all engines operating. This “rotation” can cover a time period of up to 15 seconds. This produces maximum performance, and minimum runway used. Varying from this precise technique can have catastrophic consequences – in swept wing jets! When young CFIs began using this term in Cessna 150s and the like, I thought it was a complete affectation and it made me want to throw up. It still does, but now everyone uses it! I don’t bother making the correction anymore, but deep down inside, it still produces the same feeling as chalk on a blackboard. It’s “just plain wrong!” My own oft-stated technique with any GA airplane is to allow the airplane to assume a takeoff attitude and let it fly when it wants to, just above the stall. What is the takeoff attitude? With a high-wing, it can be judged by the angle of the lower surface of the wing against the horizon. With a Bonanza, the nose gear oleo strut can be extended, a position that’s very easy to feel. This works very well with any nose-dragger, but calls for a tiny bit (say two tries) of experience with the tailwheel on the proper end. “Slightly tail-up” is about the best way I know to say it. The idea is to have enough airspeed to lift off gracefully, not so slow that you are danger of stalling, and not so fast that you’ll unnecessarily beat up the landing gear and structure. After the airplane lifts off (or, rather, gently flies itself off), holding exactly the same ATTITUDE will yield a very slight climb and fairly fast acceleration to a cruise-climb speed, usually reaching it near the far end of the runway at about 150’. I retract the gear as soon as I’m positive the airplane will not contact the runway.
Hats off to John Deakin.
Regarding push pitch down („feel light in your seat“) upon engine failures, yes, we all know it, but still stall/spin is prevailing too often. So something’s up. My bet is it’s our panic lizard brain which says „I don’t like what I see on the ground, I don’t want to crash here… let’s go up…“ and we try to extend the glide and pull the plane to a further spot.
Typical climb speeds + engine failure = <10 seconds to stall.
There’s a video by a controversial instructor out where he claims he secretly switched off the fuel selectors during taxi, to surprise pilots with an engine failure during take off. In 99% (he claims) he had to intervene to avoid a stall/spin.
The quoted passage is excellent!
I was asked to approve “tundra tires” on a Cessna 182T. I said that I would, but I would also flight test the airplane for design compliance. Now I really did not need to fly the plane to know that the oversized tires would work, but I did want to fly the plane in the company of the owner, to try to figure out why anyone would want oversized tires on a very new, glass cockpit 182T, when I knew that he commuted in it (so presumably wanted better cruise speed). I first saw the airplane in the hangar when it was in for major repairs. Nose fork bent so badly that the [standard] nose tire was scrubbing inside the fork, and obvious structural damage at the firewall and fuselage sides. Not only had owner bent it landing into a soft grass runway, but after getting it unstuck, he flew it home that way!
So airplane gets modified with the large wheels, and meet the owner for a test flight (I’m secretly testing him, not the plane!). “Hey, I’ll sit right seat, take me for a few circuits and we’ll test it out!”. Well, he had the plane up to 70 knots with all three wheels still on the runway, with the airplane totally squirming to be airborne. He muttered “rotate”, and the airplane leaped into the air with all kinds of quasi controlled thrashing. His landing was similar in lack of grace. I asked him to show me a soft field takeoff – still no use of flaps, though this time the three wheels were only in contact with the runway until 65 knots, outcome about the same.
I asked to try: 20 flap, control wheel fully aft, open the throttle, and as the nose rises a little, hold it there and wait. The airplane seamlessly lifted off around 55 knots, and transitioned nicely to acceleration and a climb. He turned to me with shocked surprise and said: “Wow, I didn’t know it could do that!”. I suggested some more training, though graciously declined to offer it myself. He crashed the airplane twice more in the next two years, once landing it very hard quite iced up, and a second landing accident which wrote it off. He didn’t seem to hurt himself either time (A testimonial to Cessna ruggedness). I see him on the TV news every now an then in his professional capacity (nothing whatever to do with aviation) and he’s apparently pretty good at his job. But I did experience a 182 being forcibly held on the runway, to “rotation” speed.
When you’re flying amphibious floatplanes, it’s really good to get the nosewheels off as early as possible. Those rather small tires carry quite a load, and spin up like crazy if you leave them on the runway. I have burst one on a very hot day, after doing numerous quick circuits over several hours (EASA noise test). I think I did not allow the tire to cool enough between landings.
In a typical SEP GA it takes around three or four seconds for turbulent separation during a stall, and what people perhaps forget, it takes a similar amount of time to ‘reattach’ lift assuming correct stall recovery technique. Altitude loss during recovery is larger with a clean wing, which a few clubs seem to encourage for take off, despite the POH in a lot of types calling for take off flaps. In the context of a full stall with a clean wing you probably need around 300 feet to recover without mushing into a deeper secondary stall. In addition as you climb out of ground effect there may be a tendency to increase alpha to maintain performance, effective alpha being higher in ground effect.
Perhaps the EFATO training in an SEP might need some refinement? Typically a ‘fan stop’ as it is called in the UK occurs around 500 feet AGL when the aircraft is at Vy or even cruise climb. There may be enough energy that the student may not even have to move the control column forward to establish best glide and select a field.
A more scientific examination of recovering from a departure stall at Vx, recovery being without power, at a safe altitude might be useful. First it would illustrate the nose high attitude of Vx with flaps up, effectively only a few knots above the stall. Secondly, with the flaps up, the period from buffet to full stall is a few seconds, less with some approach flaps. Thirdly, and perhaps most importantly, it would illustrate what a change of attitude is required, and how long it takes for the wing to start flying again, when recovering aerodynamically without power from a Vx departure stall.
The departure stall is on the syllabus but not properly understood in the context of an EFATO, and from my experience, rarely examined in the stall exercises.
RobertL18C wrote:
Perhaps the EFATO training in an SEP might need some refinement?…..A more scientific examination of recovering from a departure stall at Vx, recovery being without power, at a safe altitude might be useful. First it would illustrate the nose high attitude of Vx with flaps up, effectively only a few knots above the stall. Secondly, with the flaps up, the period from buffet to full stall is a few seconds, less with some approach flaps. Thirdly, and perhaps most importantly, it would illustrate what a change of attitude is required, and how long it takes for the wing to start flying again, when recovering aerodynamically without power from a Vx departure stall.
Exactly, and with two critical elements added:
One:
Generally, and to some degree, a GA plane needs to be at or faster than “best glide” speed at the point that the flare is begun to allow the pilot to arrest the rate of descent, and touch down as a “landing” rather than a crash. If the engine failure occurs while climbing at Vx, it will be necessary to not only immediately transition to a glide, but to also use that glide to accelerate to “best glide” speed. That will mean giving up even more precious altitude, and pitching more nose down to accelerate to the faster speed. That added step would not be required, or at least very much less so, if the airplane is actually at or faster than Vy when the engine stops.
And “best glide” is a fuzzy figure. For my experience, unless otherwise stated, it is optimum for a clean airplane to travel the greatest distance per altitude lost – sure, that makes sense. But it may not be “best” to position the airplane at the top of flare to arrest the rate of descent. That speed, for average pilot skill, is probably faster. It will be faster if the airplane is being flown in a more draggy configuration. Gross weight increase, floats, skis or cargo pod installed, or propeller change two to three blade will result in the need to increase your glide speed to store extra margin for a flare and landing – and the modification may not tell the pilot this.
Example: Cessna 182Q POH “specified” glide speed = 70 KIAS. During testing, the modified 182Q, at 3350 pounds, on amphibious floats, with wingtip extensions, three blade prop, and Golmozig exhaust had to be glided at a minimum of 80 KIAS to achieve consistent safe power off landings. I published this in the Flight Manual Supplement for that configuration, as well as a warning, as it was not otherwise presented to the pilot.
Two:
Practice forced approaches where power is returned at 100 feet, and go around teaches nothing about what energy should be stored in the plane (as airspeed) to achieve a decent flare and touchdown.
Practice power off landings from downwind to touchdown in whatever you fly.
That’s an advantage we have here at Værnes – ENVA, the runway is 2900m long. That means that part of our regular training include what the locals call touch’nGo with cut, basically you land the aircraft put take off power and take off again and then the instructor simulate an engine failure when he sees fit and the student lands the plane back on the remaining runway, and takes off again and repeat.
When I did my initial training at LFOL, we never did that, just did simulated engine failure, down to probably a 100’ but never landed back again since that would have meant damaging the aircraft significantly (the runway there is 720m long).
But the best for this type of training for me remains my seaplane flying in Como, there you can repeat the exercise of landing, taking off, simulated engine failure, landing to complete exhaustion of the pilot before your even half way though the lake :-)
Pilot_DAR wrote:
Generally, and to some degree, a GA plane needs to be at or faster than “best glide” speed at the point that the flare is begun to allow the pilot to arrest the rate of descent, and touch down as a “landing” rather than a crash.
The problem is to know what the best glide speed with landing flaps is. I have yet to see that figure in a POH. If you keep the clean best glide speed to the flare with landing flaps in an aircraft lika a PA28, you’ll float forever. (In that case the clean best glide is 78 KCAS, while the recommended approach speed with landing flaps is 68 KCAS.)
Some types the POH states a best glide, and a forced landing energy speed. For example the Beechcraft Bonanza states 105 KIAS best glide, and 83 KIAS when approaching the forced landing site.
Some types do stipulate best glide with flaps, for example the C182 has a best glide of 75 KIAS with no flaps, and 70 KIAS with flaps.
In both these examples the speeds are above Vat, or at the threshold when rounding out for the landing flare.
