MauleSkinner
Touchdown! Greaser!
Either one is a compromise. Just depends which aspects you feel are of more value. And the answer may be different at different airports or under different conditions.
Engine Failure on Takeoff
- Thread starter azpilot
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write-stuff
En-Route
A good point to consider. Vx keeps you closer to the departure runway, but Vy gets you to a "safe" altitude more quickly. I use Vx on short runways where a turnback might be an option.
Matthew Rogers
Ejection Handle Pulled
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Matt R
I have done testing in my C150 (but not at full aft CG yet) and when it is trimmed for takeoff and climb at Vy or Vx ("hands off"), it will not stall or even chirp the stall horn if power is immediately cut. The nose will fall on its own if you are not actively pulling back and it will pick up airspeed above Vy to begin is set of phugoid oscillations to return to its trimmed airspeed. What does this mean? If you don't have a death grip on the yoke and let the nose of the plane do what it wants in a departure engine out scenario, you eliminate(/reduce) the risk of a stall. There is no need to push the yoke over heavily to prevent the stall, it does it all on its own.
Now other plane, other scenario, extreme aft CG - maybe its different. Practice in your airplane. (wherever you feel safe - 2-3000' over an airport?) Its fast to do, just do a full power climb at Vx or Vy, trim for normal takeoff to hold that speed, and immediately pull the power back to idle while not manipulating the yoke and see if your plane lets the nose drop fast enough. A few others here have also done this test including in a Pitts (the complete opposite of a C150).
Now other plane, other scenario, extreme aft CG - maybe its different. Practice in your airplane. (wherever you feel safe - 2-3000' over an airport?) Its fast to do, just do a full power climb at Vx or Vy, trim for normal takeoff to hold that speed, and immediately pull the power back to idle while not manipulating the yoke and see if your plane lets the nose drop fast enough. A few others here have also done this test including in a Pitts (the complete opposite of a C150).
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Albany Tom
In the sense that you're closer to stall at Vx than Vy, then yes, KE matters. The difference in kinetic energy between Vx and Vy in most GA aircraft is very small. Like the difference in 100' of altitude small. But it does mean enough extra energy that reaction time is different, and maybe critically so depending on aircraft, loading, trim, pilot, etc.
On the other hand, if you lose the engine at the same time from liftoff, Vy vs Vx, you could be 25% or more farther away, depending on the speeds/rates of your aircraft. Agree that the shorter distance, like any altitude difference, means NOTHING if you stall the aircraft. It's very much a numbers game, and again, aircraft dependent.
steingar
Taxi to Parking
I'd love to do Vx climbs, but my aircraft tis notorious for engine heating issues. Jus told technology before they really understood how to do these things. I transition to Vy as soon as I get the gear up. Vx would make me sweat less, but I'll break the airplane if I keep doing it.
azpilot
Line Up and Wait
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azpilot
At what point do you transition to Vy?
write-stuff
En-Route
For me, I only do this on short runways where a turnback >might< be an option. In that case, I climb at Vx to roughly 700 feet, then on to Vy. My turnback altitude is about 900 feet in areas without ground obstructions. The turnback window closes at about 1500 feet since I'm then too far from the runway.
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Albany Tom
I'm similar to the above, Vx where there aren't a lot of other options. But in that situation I'll also usually do a downwind departure, and turn crosswind around 300' below pattern if there aren't any restrictions on that. By the time I'm at the opposite numbers in the pattern my thinking is I have a good indication that "all is good", and I'll fly out. Probably overly cautious, chances are slim I'll ever need this, but it's also very low cost for this.
For most takeoff's that aren't short field, I don't do this. Most airports where I go have farms around them.
For most takeoff's that aren't short field, I don't do this. Most airports where I go have farms around them.
Here's John Deakin's take on this, in Pelican's Perch #19:
"My pet peeve in climbs is using too low an airspeed. One famous training organization insists on using 95 knots to 1,000 feet AGL in a Bonanza, most of the twin operators push for a climb at or near the blue line, and virtually all the transport operators use a V2+10 climb with all engines operating. I think it’s stupid to climb that slowly in any airplane (including jets, just so I offend everyone here!) once actual obstacles are cleared.
95 knots in a Bonanza runs the engine temperatures up. Yes, they may remain within limits, but why get any hotter than necessary? Additionally, the nose will be so high you simply cannot see where you’re going – you’re blind to traffic that may very well be in your path. Finally, I firmly believe that if a total engine failure occurs at 95 knots in a Bonanza below a few hundred feet, most pilots will stall before they can get the nose down enough to maintain flying speed. If they just happen to succeed at that, they will probably end up so slow and descending so steeply that there isn’t enough energy left to flare. A crash, and an ugly one, is all but inevitable. At such low speeds, with the usual nose-high attitude, a recovery from an engine failure is very nearly an acrobatic maneuver, and not one pilot in a thousand has practiced it with any realism. It’s a bad deal.
For this reason, I prefer to see a very early shift to a higher climb speed once real obstacles are cleared. In the absence of real obstacles, I set up a gradual climb right from liftoff, pulling the gear up as soon as I am well clear of the ground (Oh, boy, I’m gonna get mail on that one! Hmm, might be a good subject for a column?) In the Bonanza, I accelerate to about 120 knots, reaching that speed by the time I’m at 100 feet AGL, or 200 AGL. This gives much better cooling, much better visibility, and makes the engine-out case far more manageable (single or twin). Yes, yes, I know, I’ll be at a slightly lower altitude when the engine quits, but not as low as you might expect. Some are very fond of quoting the sharp rise in drag with higher speed, but an often-missed factor is the improvement in prop efficiency that also takes place. The real result is that the actual climb rate on a Bonanza will suffer very little. The angle of climb (gradient) drops, of course, and it is possible for this to become a terrain clearance issue."
https://www.avweb.com/flight-safety/pelicans-perch-19putting-it-all-together/
"My pet peeve in climbs is using too low an airspeed. One famous training organization insists on using 95 knots to 1,000 feet AGL in a Bonanza, most of the twin operators push for a climb at or near the blue line, and virtually all the transport operators use a V2+10 climb with all engines operating. I think it’s stupid to climb that slowly in any airplane (including jets, just so I offend everyone here!) once actual obstacles are cleared.
95 knots in a Bonanza runs the engine temperatures up. Yes, they may remain within limits, but why get any hotter than necessary? Additionally, the nose will be so high you simply cannot see where you’re going – you’re blind to traffic that may very well be in your path. Finally, I firmly believe that if a total engine failure occurs at 95 knots in a Bonanza below a few hundred feet, most pilots will stall before they can get the nose down enough to maintain flying speed. If they just happen to succeed at that, they will probably end up so slow and descending so steeply that there isn’t enough energy left to flare. A crash, and an ugly one, is all but inevitable. At such low speeds, with the usual nose-high attitude, a recovery from an engine failure is very nearly an acrobatic maneuver, and not one pilot in a thousand has practiced it with any realism. It’s a bad deal.
For this reason, I prefer to see a very early shift to a higher climb speed once real obstacles are cleared. In the absence of real obstacles, I set up a gradual climb right from liftoff, pulling the gear up as soon as I am well clear of the ground (Oh, boy, I’m gonna get mail on that one! Hmm, might be a good subject for a column?) In the Bonanza, I accelerate to about 120 knots, reaching that speed by the time I’m at 100 feet AGL, or 200 AGL. This gives much better cooling, much better visibility, and makes the engine-out case far more manageable (single or twin). Yes, yes, I know, I’ll be at a slightly lower altitude when the engine quits, but not as low as you might expect. Some are very fond of quoting the sharp rise in drag with higher speed, but an often-missed factor is the improvement in prop efficiency that also takes place. The real result is that the actual climb rate on a Bonanza will suffer very little. The angle of climb (gradient) drops, of course, and it is possible for this to become a terrain clearance issue."
https://www.avweb.com/flight-safety/pelicans-perch-19putting-it-all-together/