Climbout - single engined...

[9 lives]

So I have asserted myself about allowing a tricycle aircraft (other than a T tail Piper) to find it's own way off the surface during takeoff. That said, I do not intend that pilots then attempt to climb away at a slower airspeed. There is probably a speed to aim for after takeoff, stated in the flight manual, which may be Vy.

Yes, the plane will climb at a slower forward speed, and perhaps seemingly quite well, but caution...

Using speeds (kts) from the C 182T flight manual (maximum weight, flaps zero unless stated): "Takeoff Normal Climbout" = 70-80, Best rate = 84, Best angle = 64, and "Best glide" = 75.

Let's say your engine goes bang at 50 feet up after takeoff; you're pointed up, slowing down until you get the nose down, and per the flight manual, you'd like to be flying at at least 75 for a gliding landing.

If you were climbing away at the 80 (fast side of the "normal climbout" range, or better yet, Vy of 84, you have either 5 or 9 kts to "spend" to enter a glide, and ease the plane back on to the remaining runway with your awesome skill.

If, however, you were impressing the onlookers with a needless climbout at Vx, you're flying at 64 kts - the the bang still happens at 50 feet. you push, and start going down. You will be well on your way down, as you attempt to accelerate to the desired 75 kts "best glide" speed. But, you're going to contact the ground first. When you did, you did not have any reserve of speed with which to flare, and arrest your descent. So a hard, damaging, and injurious arrival. At the very least, a destroyed plane.

When climbing out of ground affect altitude, if you have the room to spare, speed is your friend a little more than altitude. And speed is certainly more your friend than the awe of the crowd!

You can experiment safely with this in the practice area, with a "hard deck" of a few thousand feet. Pull the power 50 feet above your hard deck at differing speeds - see if you can flare so as to not pass through your hard deck altitude with an unarrested descent rate. This cannot be practiced safely near the ground with a reserve of safety.

[Big Pistons Forever]

I teach Vy climb to 1000 AGL for the reasons Step described above.

[Above The Clouds]

Step Turn
If, however, you were impressing the onlookers with a needless climbout at Vx, you're flying at 64 kts - the the bang still happens at 50 feet. you push, and start going down. You will be well on your way down, as you attempt to accelerate to the desired 75 kts "best glide" speed.

The only time you need to climb a Vx would be to clear a close in obstacle once clear accelerate to Vy.

That said if the engine goes bang at 50ft in the conditions you described as long as the pilot is mentally prepared for the failure they are only approx. 30ft above the flare so its reasonable to accept a successful landing is achievable.

Using the same scenario with the failure at 100-200ft that could be a different outcome for the unprepared.

[S-Works]

We only teach Vx for use in obstacle clearance circumstances and it's accelerate to Vy as soon as safe to do so.

Vy is normal format.

[Chesty Morgan]

Originally Posted by Step Turn

If, however, you were impressing the onlookers with a needless climbout at Vx, you're flying at 64 kts - the the bang still happens at 50 feet. you push, and start going down. You will be well on your way down, as you attempt to accelerate to the desired 75 kts "best glide" speed. But, you're going to contact the ground first.

Why do you need to get to best glide speed? You won't be going for distance from 50'.

[Martin_123]

wait, isn't your best glide speed meant to cover as much distance per loss of altitude? If my engine goes bang at 50ft I don't care for my glide speed, I care for my stall speed - that runway is running out fast so in the event of a bang, I want to be at 64 rather than 75, nose down, flaps out etc, quite the opposite from things you typically want when your engine goes at 2000ft and 2 miles of shore. Am I wrong?

[wanabee777]

The various V speeds referenced are all based on an assumed gross weight which will be, percentage wise, in a light aircraft, quite different when the student is flying solo rather than flying dual with an instructor or passenger(s). Even more so if the student was squeezed in with a 16 stone bloke like myself.

What's needed for a true determination of wing performance is a reliable and accurate AOA indicator.

Based on a given configuration, (ie flaps retracted), the best rate, best angle, best glide, and stall angle of attacks are independent of gross weight and all easily depicted on an AOA indicator. Best range and best endurance angle of attack likewise.

JMHO

[Pace]

wait, isn't your best glide speed meant to cover as much distance per loss of altitude? If my engine goes bang at 50ft I don't care for my glide speed, I care for my stall speed - that runway is running out fast so in the event of a bang, I want to be at 64 rather than 75, nose down, flaps out etc, quite the opposite from things you typically want when your engine goes at 2000ft and 2 miles of shore. Am I wrong?

Martin

Flying is all about energy and drag management. You basically have two sources of energy! One from the engine and the throttle controls that the other from the potential energy in the airframe and the elevator controls that.

with a failed engine you have one source of energy and that is in the airframe and trading altitude for airspeed i.e. you become a glider.

Your enemy in this situation is drag so you keep away from adding drag until you need to steepen your approach to a landing or get rid of excess energy which without drag will lead to excess speed or energy

So in an engine out situation don't think speed but energy. The higher speed you have the more energy you can tap into and the less altitude you need to trade for that energy.
As the AOA increases so does the drag. At fifty feet its more important to keep the aircraft flying and take what you have. Don't just try to land ahead into wind when there is a perfectly good field 90 degrees left or right but most important keep it flying and thats energy and drag management
The nearer the stall you are the more drag you are dealing with and the more altitude you will have to trade
Speed to a certain extent is your friend

Pace

[Chesty Morgan]

At 50' it's a moot point. Stick the nose down, maintain whatever speed you have, land. Trying to get to best glide speed at that height is a) not achievable, and b) not required.

I take it you stay on the runway until Vmbe, you know, just in case?

Edit: best glide speed doesn't equate to minimum drag either! Minimum drag is less than best glide speed and probably what you want to be aiming for assuming you have time to do anything about it.

[Pace]

For the modern pilot this clip posted on another thread is very revealing on how your brain should work especially for Cirrus drivers

https://www.youtube.com/watch?featur...&v=T_T_nINO0e4

Pace

[9 lives]

wait, isn't your best glide speed meant to cover as much distance per loss of altitude?

Yes! Which we are probably not trying to do in a return during the initial climbout - you'd rather be flying a little faster than "best glide speed".

that runway is running out fast so in the event of a bang, I want to be at 64 rather than 75, nose down,

The runway is running out, I agree, and I hope there is a surface ahead suitable for landing on. If you're gliding toward a rock face, then yes, slower is better. Otherwise....

If you are struggling up at 64 kts, and it quits suddenly, several bad factors will combine to ruin your chances of a safe return. Remember, chances of survival are inversely proportional to angle of arrival. when you get close to touching down, it'll go better if you're flying as nearly parallel to the surface as possible - you would rather arrest your descent rate with your control in the air, than the sudden ground at the bottom.

Continuing on with the C 182T speeds I started with, I neglected to include flaps up stall speed for that [maximum] weight = 50 KIAS. So you're sitting at 64 kts, nose way up, and it stops. you instantly think OMG!, and lower the nose. As the nose lowers, you're losing altitude, and a bit of speed, until you actually get the plane pointed down. Finally, you have the nose pointed down, and acceleration is imminent - at your at the ground! It's going to be a no flare crash with this kind of arrival angle:



You can see from the set up angle of the aircraft to the ground, that it's near close to level. I can certainly imagine getting into that angle if you'd just pushed sharply to maintain what little flying speed you'd had, after an engine failure during climbout. But the descent was not arrested. It ended badly.

In other threads we have agreed that controls will be somewhat less effective at slower speeds. So, pulling hard to flare, when ground contact is imminent, might not result in the immediate change in attitude and descent angle desired for a gentle arrival. Once you're descending, whether you commanded it, or the plane did it anyway, flaring is going to take some vertical space, and airspeed to give up, to accelerate away from your downward path, and you're out of both!

When I started flying Cessnas with STOL kit cuffs on the wings, I found that they had a slower stall speed (as intended), and yes, they will glide at a slower speed too! But if you try a slower glide speed for short final, you're in for a nasty surprise, as you will have even less stored energy with which to arrest your descent for a gentle flare.

I opine that "best glide speed" is a single value determined to achieve the greatest distance forward for altitude lost. This speed will be on the slow side for allowing you the reserve of speed (your stored energy) to allow you to flare nicely at the bottom. So carry the extra speed if you have the choice - before the engine fails.

[foxmoth]

I do not even understand why this is a thread, as others have said, best angle is for obstacle clearance, once that is obtained then best rate gets you height if any problems - height is your freind. As far as speed goes, I would agree that this is a secondary factor at 50', though you do NOT want to stall, so getting the nose down is important, but at the same time, too much speed may give you a much longer landing than you want, as you get higher correct glide speed becomes more important.

[Martin_123]

I suppose it makes sense if you're at 50 feet.. However you're only there for a short second, what if it fails at 200 - 300 feet? The whole premise of engine dying at precisely 50ft with different airspeeds may not be fair - if the engine is bound to fail, it will probably fail after x amount of time after applying full power rather than height. Thus the question really is - if your engine is dying in 60 seconds after applying full power, where would you rather be - 64kt @ 100 ft or 75kt @ 50ft? Having speed is nice.. having altitude is even nicer, isn't it?

[Pace]

I would rather be at 75KTS and have the altitude too
At 50 feet I would rather be at 75KTS than 64 KTS
Give me energy any time and drag to add when I don't need that excess energy anymore

Pace

[9 lives]

height is your freind

Not absolutely.... I would rather be at a reasonable height, and have a nice margin on the glide speed, than to be higher, and flying no faster than the best angle, or glide speed. The transition from going up at high power, to entering a stable glide, will consume altitude, which you would rather minimize. Flaring at the bottom will consume airspeed, which you would rather have in excess when you get there!

[Crash one]

Height is only your friend if you have room to manoeuvre and lose it under control. If you are on a short strip with trees at the end I would rather be as low and under control as possible. I'll settle for "min control speed" rather than best glide, Vx, Vy, or whatever. This 50 ft scenario depends on what is underneath/ahead.

[mikehallam]

The video above isn't a very good example of a heavy landing at all, because the 'runway' has been so tampered with that the poor nose-wheel just buries itself, rather than having at least half a chance of compressing horribly.

Second observation is that the belted pax seemed just as badly off as the unrestrained P1. Maybe slower frames per sec. would tell more.

Anyway as support for the arguments being propounded on this thread it is pretty useless, maybe someone has a better one nearer true conditions they could put up ?

mike hallam.

[Chuck Ellsworth]

So carry the extra speed if you have the choice - before the engine fails.

And put an AOA indicator in your airplane.

[Gertrude the Wombat]

where would you rather be - 64kt @ 100 ft or 75kt @ 50ft?

Whichever is less energy so that I'd have more chance of getting it down and stopped before the runway's gone. I'm afraid my mental arithmetic isn't up to working that out in a couple of seconds, I'd need pencil and paper to do the sums.


(edit)


Right, in fact there's not a lot in it but 64kt @ 100ft looks like being about 6% less energy. So assuming I shove the nose down fast enough not to stall then that's the winner.


*** BUT *** that's just the total energy at the point of engine failure. There's then how fast you use it up on the way down, which will be speed dependent, and at different speeds there will be different effects from the headwind ... no, I'm not doing the next set of sums just right now.

[FullWings]

I suppose one thing you can definitely say about a failure of this kind is that it is well worth taking a few seconds thinking about the possibility before you start the takeoff roll.

In terms of dynamics, as soon as you lose power, you will start losing airspeed and this will continue until until you reduce your pitch attitude at least to that required for a steady glide at your current airspeed. If you do this too slowly you may not have enough left to flare with any great success.

Here’s an example of power loss at 100’ in a much cleaner aircraft than the average SE GA example. The pitch change needed is substantial until the speed recovers...