Fake it till you can make it.

[tgrayson]

Shallow = good = airspeed first (not =) stall spin crash burn after powerplant failure in heavier single.

Depends. Since altitude and airspeed are interchangeable, the safest course is to maximize the total of the two, rather than one or the other. There is a way of expressing airspeed in terms of altitude by calculating how high you could zoom if you pulled back on the yoke until you achieved a zero airspeed. If you make these calcuations, it turns out that you maximize the energy of the aircraft by accelerating to Vy as quickly as you can and climbing at that airspeed. The increased kinetic energy you get by accelerating to a faster speed is less than what you'd get by investing the power into additional altitude, and the difference increases every second. You can always turn that altitude into airspeed if you need to. Altitude is an investment and airspeed is an expense past Vy.

 

[ppragman]

Depends. Since altitude and airspeed are interchangeable, the safest course is to maximize the total of the two, rather than one or the other. There is a way of expressing airspeed in terms of altitude by calculating how high you could zoom if you pulled back on the yoke until you achieved a zero airspeed. If you make these calcuations, it turns out that you maximize the energy of the aircraft by accelerating to Vy as quickly as you can and climbing at that airspeed. The increased kinetic energy you get by accelerating to a faster speed is less than what you'd get by investing the power into additional altitude, and the difference increases every second. You can always turn that altitude into airspeed if you need to. Altitude is an investment and airspeed is an expense past Vy.

I agree with you up to the bolded text. In a very heavy SE airplane, I want a margin of error for action calculated in time before I stall, not in altitude. In the 207 for example, I climb at Vy to 400AGL then 100kts, why? Vy gives me book recommended Vglide for take off. Then above 400' I want to have time to think about what I'm doing without having to make any aggressive moves. At 100kts, you have 20kts at 3800lbs (MGTOW) with flaps up to make a decision, and or figure out whats going on. At 87kts, you have to immediately throw the nose over, and it will be a fairly aggressive change. I don't want to do anything aggressive when my problem could be as easy as "switch tanks, boost pump on."

100kts gives me a chance to think before immediate action. I'm not saying climb out at a ridiculously low angle, but speed is life when seconds count. How fast can you identify an engine failure when you're not really expecting it. Its not an instantaneous thing. Engine failures are not all the same thing either. Many of them are partial power failures (most mechanically induced failures if the stats I've seen can be trusted). By far most of them are pilot error (e.g. fuel = 0 in that tank). At 100kts you can wait for 80 while trying to switch tanks real quick. Then once you've got 80, if the thing won't light off, you're still at your same altitude, and you've exhausted most of the trouble shooting you can do. If you're climbing out at 87kts, you have to immediately and aggressively pitch for 80, otherwise you'll be slower than best glide. Just my $.02.

As for the physics of it, I completely agree with you, the best way to maximize both is Vy, but I'm not looking for only altitude or airspeed, I'm looking for time too.

 

[jrh]

As for the physics of it, I completely agree with you, the best way to maximize both is Vy, but I'm not looking for only altitude or airspeed, I'm looking for time too.

If you maximize both airspeed and altitude as tgrayson explained, you'll end up with maximum time from the point of engine failure to the time of touchdown on the ground.

 

[MikeD]

If you maximize both airspeed and altitude as tgrayson explained, you'll end up with maximum time from the point of engine failure to the time of touchdown on the ground.

I like extra speed for maneuvering purposes, as my landing area may not be straight ahead +/- 20 degrees. Really, it's a potato, po-ta-to discussion here. You guys all have fine techniques, each of which has it's own particular benefits and limitations, proper for different operating scenarios and equipment.

Through my mil career, I've been a speed guy on T/O......always want speed to trade into zoom climb to punch out with a positive vector if at all possible; helping the seat save you being the operative thing.

Different techniques for different ops. The key: be flexible.

 

[jrh]

I like extra speed for maneuvering purposes, as my landing area may not be straight ahead +/- 20 degrees. Really, it's a potato, po-ta-to discussion here. You guys all have fine techniques, each of which has it's own particular benefits and limitations, proper for different operating scenarios and equipment.

But the thing is, from a strictly physics perspective, carrying extra speed beyond Vy is wasting energy. It might "feel" better, but it's an old wives tale. Ppragman's talk of a heavy aircraft doesn't make sense. Aircraft weight has nothing to do with this scenario, other than shifting Vy to a faster speed. The fact remains, climbs at Vy are still the most efficient way to maximize kinetic and potential energy at any moment during climbout. I'd be interested to hear any explanations to the contrary.

Having the most total energy (potential + kinetic) is what is needed, *especially* if the best landing site is not straight ahead.

Through my mil career, I've been a speed guy on T/O......always want speed to trade into zoom climb to punch out with a positive vector if at all possible; helping the seat save you being the operative thing.

I'll start speeding up as soon as they start mounting ejection seats in Cessnas

But seriously, that detail makes a huge difference. Unless I'm wearing a chute and above 2000 AGL, I have to ride the bird down. In your military aircraft, you don't.

Different techniques for different ops. The key: be flexible.

Maybe I'd be more flexible if a more logical argument were presented than "extra speed keeps the plane further away from a stall."

A stall is preventable. Don't pull back and the plane won't stall. I don't worry about stalls after an engine failure as long as the pilot has the instincts to unload the wing and keep flying.

Landing sites, on the other hand, are more troublesome. The way to have the best options is to have as much energy as possible--requiring a climb at Vy.

 

[MikeD]

But the thing is, from a strictly physics perspective, carrying extra speed beyond Vy is wasting energy. It might "feel" better, but it's an old wives tale. Ppragman's talk of a heavy aircraft doesn't make sense. Aircraft weight has nothing to do with this scenario, other than shifting Vy to a faster speed. The fact remains, climbs at Vy are still the most efficient way to maximize kinetic and potential energy at any moment during climbout. I'd be interested to hear any explanations to the contrary.

Having the most total energy (potential + kinetic) is what is needed, *especially* if the best landing site is not straight ahead.

It depends. That's what I'm trying to get through to you guys...there's no "one right way" to do anything. In most situations, Vy is great. Operations-wise, terrain-wise, site availability-wise; might dictate different.

I'll start speeding up as soon as they start mounting ejection seats in Cessnas

But seriously, that detail makes a huge difference. Unless I'm wearing a chute and above 2000 AGL, I have to ride the bird down. In your military aircraft, you don't.

Yes it does.....was just giving an example of when differences may play a part in what you're doing when.

Maybe I'd be more flexible if a more logical argument were presented than "extra speed keeps the plane further away from a stall."

A stall is preventable. Don't pull back and the plane won't stall. I don't worry about stalls after an engine failure as long as the pilot has the instincts to unload the wing and keep flying.

Landing sites, on the other hand, are more troublesome. The way to have the best options is to have as much energy as possible--requiring a climb at Vy.

See above. It depends. Even more so on when an engine failure occurs. Again, Vy is fine...good to do. Some may prefer to have 10 more knots of airspeed (an arbitrary number, for our purposes here) and a little less altitude (who knows by how much) to have a little more maneuverability, especially if attempting turns in a heavyweight a/c where you don't want the VVI to radically increase (personal experience from my own T-207 days....engine failure, needed to make a landing area over 90 off the nose, the extra speed allowed the turn....to be able to bleed to Vy/glide and complete the landing ). Provides a little more margin in that circumstance....ie- that airport, with that terrain, in that situation. All are good techniques for their intended purposes and situations.

 

[ppragman]

If you maximize both airspeed and altitude as tgrayson explained, you'll end up with maximum time from the point of engine failure to the time of touchdown on the ground.

Touchdown on the ground isn't what I'm trying to keep from doing, I want to maximize the time before I have to start descending.

But the thing is, from a strictly physics perspective, carrying extra speed beyond Vy is wasting energy. It might "feel" better, but it's an old wives tale. Ppragman's talk of a heavy aircraft doesn't make sense. Aircraft weight has nothing to do with this scenario, other than shifting Vy to a faster speed. The fact remains, climbs at Vy are still the most efficient way to maximize kinetic and potential energy at any moment during climbout. I'd be interested to hear any explanations to the contrary.

Having the most total energy (potential + kinetic) is what is needed, *especially* if the best landing site is not straight ahead.



I'll start speeding up as soon as they start mounting ejection seats in Cessnas

But seriously, that detail makes a huge difference. Unless I'm wearing a chute and above 2000 AGL, I have to ride the bird down. In your military aircraft, you don't.



Maybe I'd be more flexible if a more logical argument were presented than "extra speed keeps the plane further away from a stall."

A stall is preventable. Don't pull back and the plane won't stall. I don't worry about stalls after an engine failure as long as the pilot has the instincts to unload the wing and keep flying.

Landing sites, on the other hand, are more troublesome. The way to have the best options is to have as much energy as possible--requiring a climb at Vy.

I'm not arguing that your way is more efficient for gaining height. I know where I'm going to land in all these scenarios where I normally fly. If I was taking off out over the open ocean at night or in the middle of a forest with no coast line, I would think otherwise. That being said, I want time for the airspeed to bleed off before I start to descend, therefore I don't have to agressively lower the nose for best glide.

Your way gets me an extra 200-400fpm sustained, and frankly the agressive response to an engine failure that will be required to chase Vglide is not worth it.

As for "extra speed keeps the airplane farther from stall," I fail to see what's illogical about that.

-pat

 

[jrh]

See above. It depends. Even more so on when an engine failure occurs. Again, Vy is fine...good to do. Some may prefer to have 10 more knots of airspeed (an arbitrary number, for our purposes here) and a little less altitude (who knows by how much) to have a little more maneuverability, especially if attempting turns in a heavyweight a/c where you don't want the VVI to radically increase (personal experience from my own T-207 days....engine failure, needed to make a landing area over 90 off the nose, the extra speed allowed the turn....to be able to bleed to Vy/glide and complete the landing ). Provides a little more margin in that circumstance....ie- that airport, with that terrain, in that situation. All are good techniques for their intended purposes and situations.

But that's what I'm objecting to...physics prove otherwise. I'll be the first to admit different circumstances require different courses of action. I'm all for using judgement. However, we can't change the laws of physics.

Look at it this way:

If a person climbs at Vy, they will have more altitude. Let's say they lose 10 knots of airspeed (Vy instead of Vy + 10), but gain 100 feet of altitude.

So there can be two scenarios.

Scenario 1 has a pilot climbing at Vy. A few seconds after takeoff he'll be at, say, Vy and 600 AGL.

Scenario 2 has a pilot climbing at Vy + 10. A few seconds after takeoff he'll be at, say, Vy + 10 and 500 AGL.

In the event of an engine failure, the pilot in Scenario 1 can trade that 100 feet of altitude for *more* than 10 knots of airspeed. Essentially, if he pitches down correctly, when he's at 500 AGL he might have an airspeed of Vy + 15--same altitude as the guy in Scenario 2, yet faster airspeed = more options. Time, altitude, and speed are all in the favor of the pilot in Scenario 1. It's simple physics.

Am I missing something?

 

[jrh]

Touchdown on the ground isn't what I'm trying to keep from doing, I want to maximize the time before I have to start descending.

Why is descending such a bad thing? If you climb at Vy, the extra altitude gained from the more efficient climb will more than offset any needed descent after an engine failure.

If I was taking off out over the open ocean at night or in the middle of a forest with no coast line, I would think otherwise.

Why?

That being said, I want time for the airspeed to bleed off before I start to descend, therefore I don't have to agressively lower the nose for best glide.

Your way gets me an extra 200-400fpm sustained, and frankly the agressive response to an engine failure that will be required to chase Vglide is not worth it.

I know you've talked about the 207 having some unusual aerodynamic characteristics, so there might be something I'm missing, but every piston single I've flown has been relatively straightforward when it comes to engine failures. Lower the nose to a little below the horizon and you're done. There's no reason to chase anything. I don't consider this aggressive or in any way unreasonable.

As for "extra speed keeps the airplane farther from stall," I fail to see what's illogical about that.

It's illogical because there are more important things to worry about after an engine failure, like having time to get the engine going or gliding to a suitable landing site. Both of those issues are addressed through maximizing both speed *and* altitude, not just speed alone.

 

[ppragman]

Recommended best glide is 85kts for engine failues after takeoff, Vy is 87. I'm going to have to immediately pitch over, and with a glide ratio of about 1nm for 1000' its going to be aggressive. I won't do that. I want time to think. Its slightly longitudinally unstable and the speed doesn't just correct itself with a full load. It sometimes, when you pull power off, the nose will even rise (think really really really aft CG) 500' AGL, vs. 600' AGL doesn't really give me that much extra time.

And, from a purely physics standpoint, the time for the airspeed to decrease should be the same as to descend that 100' because energy has to be conserved. KE + PE = TE. You don't win anything really.

If I'm taking off with terrain that limits a safe descent ahead and demans a 180 degree turn, I need to climb as fast as I can, whereas if there are plenty of places to land, I have more options.

 

[MikeD]

But that's what I'm objecting to...physics prove otherwise. I'll be the first to admit different circumstances require different courses of action. I'm all for using judgement. However, we can't change the laws of physics.

Look at it this way:

If a person climbs at Vy, they will have more altitude. Let's say they lose 10 knots of airspeed (Vy instead of Vy + 10), but gain 100 feet of altitude.

So there can be two scenarios.

Scenario 1 has a pilot climbing at Vy. A few seconds after takeoff he'll be at, say, Vy and 600 AGL.

Scenario 2 has a pilot climbing at Vy + 10. A few seconds after takeoff he'll be at, say, Vy + 10 and 500 AGL.

In the event of an engine failure, the pilot in Scenario 1 can trade that 100 feet of altitude for *more* than 10 knots of airspeed. Essentially, if he pitches down correctly, when he's at 500 AGL he might have an airspeed of Vy + 15--same altitude as the guy in Scenario 2, yet faster airspeed = more options. Time, altitude, and speed are all in the favor of the pilot in Scenario 1. It's simple physics.

Am I missing something?

I agree with what you're saying. Yes, Vy climb equals more altitude. By how much? Who knows, but it is more. Scenario #1 pilot has to pitch down to lose 100 (nominally speaking) feet in order to gain about 10 kts of speed. Scenario #2 pilot can remain at altitude with 10 knots pad, or dissipate that extra speed in a turn without sacrificing excessive VVI. Both are perfectly viable options, and will get you to roughly the same point. Why? Because what we don't (and really can't) factor in is pilot recognition/reaction time, how the pilot reacts (does he ham-fist the controls or smooth control), and all the other variables we talked about. The physics examples....in BOTH scenarios.....are pretty much under ideal conditions, even if pre-planned. In my incident, I didn't even have time to pay attention to my airspeed vs altitude exact figures, as I was busy working towards the landing spot I'd had picked and was flying mostly by feel and quick crosscheck. My point is that all these techniques are all correct; they will generally get you to the same point on the ground after you factor all the different variables I wrote above.

So you're not missing anything!

 

[jrh]

Ok, I see what you both are saying, but we'll have to agree to disagree.

Flying the most efficient balance of airspeed and altitude will give the most options in an emergency by every standard--time, altitude, and airspeed. I don't see how it can get any simpler than that.

If we're going to start looking at recognition/reaction times, we might as well throw both arguments out the window, because the best technique in the world won't save a pilot who is slow to recognize and react to a problem.

Also, if in our hypothetical scenario, a landing site is already assured, why are we bothering with this discussion anyway? Nobody cares about altitude or airspeed in that case--just do what it takes to land the plane and call it a day. The whole point of this discussion is to address the safest way to handle an engine failure if a landing site is *not* assured.

 

[derg]

You're supposed to fight to the death. This is a forum on the internet.

Everytime you enable someone to disagree with you without instant textual consequence, baby Jesus cries for your lost soul.

 

[MikeD]

Ok, I see what you both are saying, but we'll have to agree to disagree.

Flying the most efficient balance of airspeed and altitude will give the most options in an emergency by every standard--time, altitude, and airspeed. I don't see how it can get any simpler than that.

.

Ok. Lets toss out the other variables and just discuss this. If I'm at Vy, and I can land straight ahead with no major maneuvering, then Vy works for me since I won't have to worry about getting under Vy or having to lose excessive altitude due to maneuvering in order to maintain Vy, or even gain more than Vy itself. If where I'm going allows shallow turns, a wider turn radius and a slower turn rate; then cool. Bad thing is, I don't have the flexibility to maneuver towards an ideal landing direction in every case since my maneuverability is more limited, lest I want to impact the ground early.

At Vy +10, I maybe lower a bit in altitude (really, not a very significant amount), but have the flexibility to maneuver and extra airspeed to play with in a long turn without a significant loss of altitude or rise in vertical velocity in order to keep from going below Vy. I get more maneuverability through a faster turn rate and smaller turn radius; all dependant on where I plan to put down (assuming somewhere behind my 3/9 line). Bad thing is, I have less time to do all this, lest I hit the ground early (notice the trend?).

So it's a trade-off, and it all depends on what cards you've been dealt regards where you want to put the plane, in terms of what technique to use when. BOTH techniques worked for me depending on the situation.

Remember, there isn't one answer for all situations.

 

[moxiepilot]

You're supposed to fight to the death. This is a forum on the internet.

Everytime you enable someone to disagree with you without instant textual consequence, baby Jesus cries for your lost soul.

Cage match! Cage match! Cage match!

 

[MikeD]

Cage match! Cage match! Cage match!

Lol! Both of us are arguing very good techniques; all I'm saying is that each have their own application depending on the situation at hand.

 

[moxiepilot]

(sounding like Quagmire) Oh yeah.

I'm enjoying watching and learning. I like the debate. I couldn't argue with myself any better, not that I argue with myself. Or do I?

 

[tgrayson]

And, from a purely physics standpoint, the time for the airspeed to decrease should be the same as to descend that 100' because energy has to be conserved. KE + PE = TE. You don't win anything really.

I don't agree with your interpretation here. What you're doing is converting that extra airspeed into altitude. Achieving that extra airspeed cost you excess horsepower and once you achieved it, it required that extra horsepower just to maintain that airspeed, meaning that the extra horsepower brought you no further gains other than the initial airspeed increment. If you had used the extra horsepower to climb, you would continuously get extra altitude, rather than just getting a one-time hit as with the airspeed.

You're right that energy is converved, but in the cliimb at Vy, you end up with a much larger quantity of TE, so it's not a zero sum game at all. And you're right that at 5 or 600 feet AGL, it's not a big difference, but then you don't really know when your engine is going to fail.

And if your aircraft is longitudinally unstable at full load, then you're CG is aft of limits. If the aircraft behaves as you say, and you're within CG limits, I'd more likely suspect a re-trimming effect caused by the application or reduction of power.

 

[tgrayson]

they will generally get you to the same point on the ground after you factor all the different variables I wrote above.

Only because you assumed that the pilot reaction time magically assumed whatever value it needed to be in order to produce that result. I don't find that a reasonable assumption.

 

[tgrayson]

At Vy +10, I maybe lower a bit in altitude (really, not a very significant amount), but have the flexibility to maneuver and extra airspeed to play with in a long turn without a significant loss of altitude or rise in vertical velocity in order to keep from going below Vy. I get more maneuverability through a faster turn rate and smaller turn radius.

?? Vy+10 gives you *lower* rate of turn and a *larger* turn radius. Once again, Vy rules.