NYCY note my modifier, in the aerodynamic sense of the word.
In a soft field take off the control input is actually before Vs as you are holding the control column back – are we then in violation of the airworthiness certificate?
I would use it in the defined sense of the word by the FAA.
Of course your not in violation of the AW certificate. The only things binding on a pilot are the limitations section of the POH.
Actually, “rotate” is the manoeuvre that leads to the take off and since V_r is defined as the speed of control input, it may well be at very different speeds depending on the circumstances given. For example, on a soft field with high grass, V_r is considerably lower than V_lof. Granted, this difference may be a bit academic (well, that’s what I do) but actually if you come to think of it, it is merely a word, defined in a given context and enabling the instructor to communicate with the student on a very clear basis. If I say “rotate” on the right seat, the student on the left knows exactly what I want from him: Take the front wheel off the ground and let the plane fly away. I simply fail to see, why this very basic concept, although originating in the operation of high swept wings, should not be transferred to basic flight training in a C150. And on soft field takeoffs and / or in high density altitudes, the 150 will take her time to lift off the ground and there is a great difference between the nose wheel lift off and the main wheel lift off. Take off speed would be a very different speed.
There is one more advantage of using this concept in basic flight training: I have found that pilots, who deliberate brief before the take off “rotate with 50, she’ll fly with 60, climb out with 80” on our 172 do check the ASI during take off roll. The “50 – rotate” is a “speed alive” and gives ample room for aborting a takeoff, if the plane is felt to lift off but the ASI doesn’t show 50, or flying a circuit knowing from the very beginning, your ASI doesn’t work.
So, basically it leaves me with repeating my question to your answer:
The reason not is because it is not applicable to a single engined aircraft.
Why not?
Cheers,
hold the yoke back to relieve the nose strut and at approximately 60 it lifts off by itself.Quote
Yes! And, as it lifts off by itself, with a bit of pitch control (probably check down) it will steadily accelerate and climb. This is a plane which is “ready to fly”.
I was flying the 182 amphib again today. It will leave the ground at 50 KIAS if you want, or happily at 65. It will climb away at 55 KIAS, but this would not be good, and suicidal should the engine fail below 500 feet. Because, it will glide at 60 KIAS, but there would be zero flare or arrest of descent. I demonstrated that a glide speed of 80 KIAS is workable, but 90 KIAS will allow a suitable flare and feather soft landing. So there is a 30 knot difference in possible glide speeds. I admit that this 182 is so heavily modified, that Vx and Vy are uncertain to me, I’m going to have to confirm them during upcoming flight testing. But, it is a certainty that I will not allow a published Vy, from which a glide cannot be entered safely, and Vx will have consideration for glide entry, or a severe warning that it is not possible.
This plane, when pitched up a couple of degrees during the mid takeoff run, will seem to balance precariously on the main wheels, and be very sensitive to any pitch excursion. But, if controlled with precision, it will lift off flawlessly at 65 KIAS, and climb away perfectly. It is not being fought into the air, just flying.
The reason not is because it is not applicable to a single engined aircraft.
Why not?
Because part of the definition of Vr is that it must be equal to or greater than 1.05 of Vmca
Because part of the definition of Vr is that it must be equal to or greater than 1.05 of Vmca
For multi engine planes that is correct. However, for single engine planes, the limit is Vs1. See msg 79 of this thread, where the FAR23 definitions are set.
VS1 means the stalling speed or the minimum steady flight speed obtained in a specific configuration.
Definition
So Vr is limited EITHER by 1.05 of Vmca in ME planes or Vs1 in SE Planes. From that definition, FAR23 sais clearly that Vr is appropriate to use in SE planes.
Having established that the definition in Part 23, while relevant for Vmca, does not seem to apply in the practical operation of most SEP, the control input occurring before Vs1, if it did have a practical application wouldn’t POH for these aircraft have Vr indicated?
I was always taught that Vr was to acheive the desired Net Take Off flight path to ensure clearance of the first obstacle by the screen height following failure of the critical power unit. On that basis it would not exist in SE aeroplaners.
I see assertions that the term for rotate, Vr originated from swept wing aircraft, but where is the proof? I gave proof that at least one national authority defines the term differently and that it applies to SE aircraft.
Thank you Tumbleweed. From memory, and my ATPL theory was a long time ago, I can recall something like " pass screen height with one power plant inoperative and achieve obstacle clearance climb gradient"
That was UK CAA exams.
In any case, it is pseudo airline gibberish when used to refer to a light aircraft take-off. Ah, yes, I knew there was a word for it!
Warning thread drift……
I’ve been posting a lot lately, mostly because I have been waiting for the snow to stop to test fly my pretty little Mucha glider after C of A in Poland. Today it happened, but I still can’t take it home until some small snags are sorted. Now that is an aeroplane that really talks to the pilot. Control forces perfectly harmonised, pitch force less than 800 grams per G, impeccable visibility, soars like a homesick angel and lands in 80 metres. Not suitable for pilots who fly in boxing gloves. Take-off speed is whatever it is, there isn’t any such nonsense in the POH which concentrates on far more useful stuff, such as how to correctly attach the wings. So with luck you won’t hear from me between thursday evening and sunday, as I will be driving home with the trailer. Any glider pilots here know a more agreeable glider to fly? Don’t say standard Libelle, that is nearly as good but lacks a little aileron authority by comparison, although it has a better polar and glide angle. (don’t tell F-AZLU I said that!)
I was always taught that Vr was to acheive the desired Net Take Off flight path to ensure clearance of the first obstacle by the screen height following failure of the critical power unit. On that basis it would not exist in SE aeroplaners.
From memory, and my ATPL theory was a long time ago, I can recall something like " pass screen height with one power plant inoperative and achieve obstacle clearance climb gradient"
Sorry, but that definition is just not true. Well, memories fade. As NCY cited a couple of posts earlier:
Sec. 23.51 Takeoff speeds.
(a) For normal, utility, and acrobatic category airplanes, rotation speed, VR, is the speed at which the pilot makes a control input, with the intention of lifting the airplane out of contact with the runway or water surface.
(1) For multiengine landplanes, VR, must not be less than the greater of 1.05 VMC; or 1.10 Vs1;
(2) For single-engine landplanes, VR, must not be less than Vs1; and
(3) For seaplanes and amphibians taking off from water, VR, may be any speed that is shown to be safe under all reasonably expected conditions, including turbulence and complete failure of the critical engine.
And you get pretty much the same in European CS:
CS 23.51 Take-off speeds
(a) For normal utility and aerobatic category aeroplanes, the rotation speed VR, is the speed at which the pilot makes a control input with the intention of lifting the aeroplane out of contact with the runway or water surface.
(1) For twin-engined landplanes, VR must not be less than the greater of 1·05 VMC or 1·10 VS1;
(2) For single engined landplanes, VR, must not be less than VS1; and
(3) For seaplanes and amphibians expected conditions, including turbulence and
complete failure of the critical engine. taking off from water, VR, must be a speed that is shown to be safe under all reasonably
So basically, there IS a rotation speed in a C150, as well as in a C510. Furthermore, there are scenarios in flight training, where the concept of a defined rotating speed comes quite handy, as I have explaned above. So what does it harm to use a pretty good concept in flight training? Does is make “number pilots”? Certainly not, only the rotation, not the lift off is done at a deliberate speed. Does it produce unsafe pilots? My guess is not, because only if you anticipate a certain aircraft performance prior take off, you have means of measuring its actual performance. Just by the way of “well, let’s pull back the yoke at some time and eventually we’ll get airborne”, you have no Idea how your aircraft is performing. While this may be okay if you fly similar aircraft with similar loads from similar strips in similar weather all the time, you might be asking for trouble if you deviate from these similarities all too often. So my guess is, if our pilots have a defined rotation speed, they will sure be knowing facts about deviations from the aircraft performance before those deviations (Take off mass, density, runway quality, bad engine, etc.) run them into trouble.
Actually, without intending to be rude, I still wait for a single argument contradicting the use of V_r in flight training, or in a SEP in general. Where does it harm? Where does communication become unclear? Why should it be a reserved word, that only ATP are approved to use?
And you can’t seriously claim that a take off speed in a POH is useless and constitute this with a late 1950s gliders POH? Of course a glider has no take off speed published. (BTW: Try the Ka6Cr, or better, the Ka6E for control harmony. Unbeaten).
Cheers,
