V2 Climb question
stormyweathers, a classic example of how assumption / common practice can distort awareness, but I am catching up.
pistinaround, thanks for the update, but you still don’t specify if the SOP mandates the speed to be flown at 30 AoB with all engines. Without more info, a full explanation of the Captains choice would be difficult.
Flying the turn at V2 and 30 AoB, there would be insufficient stall margin; thus most Captains are incorrect. Also IIRC, V2 is not considered a normal operating speed.
Presumably because the need for terrain clearance, the climb speed should have a maximum value, to ensure sufficient climb gradient.
Flying at Vy gives a theoretical better performance, but the Captain’s reasoning using energy is unusual if not incorrect. There will be a need to change attitude and there may be a loss of speed depending on how dynamic the engine failure manoeuvre is. I would not expect to change speed for reasons explained in #11, #16.
Why 30 AoB AE – a good question for your performance management, as might be the general principles of why the procedure is required / authorised. More details – operations certification authority, airport?
stormyweathers, If you suddenly lose an engine, will you lose some speed? Yes.
Will you have to pitch down to recover the lost speed and regain V2? Pitch down to maintain / recover speed, this depends on flying skill and how much speed is lost.
Will you lose height as you pitch down? No, you should not. The performance requirements for V2 ensure a positive climb gradient in a turn and with OEI.
pistinaround, thanks for the update, but you still don’t specify if the SOP mandates the speed to be flown at 30 AoB with all engines. Without more info, a full explanation of the Captains choice would be difficult.
Flying the turn at V2 and 30 AoB, there would be insufficient stall margin; thus most Captains are incorrect. Also IIRC, V2 is not considered a normal operating speed.
Presumably because the need for terrain clearance, the climb speed should have a maximum value, to ensure sufficient climb gradient.
Flying at Vy gives a theoretical better performance, but the Captain’s reasoning using energy is unusual if not incorrect. There will be a need to change attitude and there may be a loss of speed depending on how dynamic the engine failure manoeuvre is. I would not expect to change speed for reasons explained in #11, #16.
Why 30 AoB AE – a good question for your performance management, as might be the general principles of why the procedure is required / authorised. More details – operations certification authority, airport?
stormyweathers, If you suddenly lose an engine, will you lose some speed? Yes.
Will you have to pitch down to recover the lost speed and regain V2? Pitch down to maintain / recover speed, this depends on flying skill and how much speed is lost.
Will you lose height as you pitch down? No, you should not. The performance requirements for V2 ensure a positive climb gradient in a turn and with OEI.
This whole discussion seems to revolve around a varying understanding of what V2 is and is not.
My take:
V2 IS a performance speed for OEI operations.
V2 is NOT a performance speed for AEO.
As previously noted, V2 is not intended to be, nor was it established as an AEO performance speed. It is a speed selected by the manufacturer to achieve the most favorable performance under the engine failure at Vef scenario used for aircraft certification purposes. Picture the segmented takeoff performance graphic taught in so many type rating courses and airline ground schools.
Since typical V2 speeds are on the order of around 1.2 times the unaccelerated stalling speed for the selected takeoff configuration, very little excess maneuvering margin is available. Hence the 15 degree bank assumption built into OEI procedures. If an engine went inop while maneuvering AOE at V2, aggressive and precise action would be required very quickly to keep the speed from approaching a very critical value. I wouldn't bet on what percentage of pilots would successfully recover to a safe speed without trading some altitude.
In any case, V2 is a OEI speed, you don't benefit from being that slow when maximum propulsion is available. So I believe the Captain who flies this unusual seeming departure at the somewhat higher than V2 speed is more correct than the ones who think V2 is the speed to fly.
That's my $.02 worth.
My take:
V2 IS a performance speed for OEI operations.
V2 is NOT a performance speed for AEO.
As previously noted, V2 is not intended to be, nor was it established as an AEO performance speed. It is a speed selected by the manufacturer to achieve the most favorable performance under the engine failure at Vef scenario used for aircraft certification purposes. Picture the segmented takeoff performance graphic taught in so many type rating courses and airline ground schools.
Since typical V2 speeds are on the order of around 1.2 times the unaccelerated stalling speed for the selected takeoff configuration, very little excess maneuvering margin is available. Hence the 15 degree bank assumption built into OEI procedures. If an engine went inop while maneuvering AOE at V2, aggressive and precise action would be required very quickly to keep the speed from approaching a very critical value. I wouldn't bet on what percentage of pilots would successfully recover to a safe speed without trading some altitude.
In any case, V2 is a OEI speed, you don't benefit from being that slow when maximum propulsion is available. So I believe the Captain who flies this unusual seeming departure at the somewhat higher than V2 speed is more correct than the ones who think V2 is the speed to fly.
That's my $.02 worth.
OBN:
Just saying that V2 is a speed computed to achieve a required performance with one engine inoperative and is not intended to be used as a "normal" or all engines operative performance speed.
Just saying that V2 is a speed computed to achieve a required performance with one engine inoperative and is not intended to be used as a "normal" or all engines operative performance speed.
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Westhawk has it right. Note that he said "for aircraft certification purposes"
Do we ever see the mention of V2 other than for this purpose? I think not.
FlightPathOBN, what does not "compute"?
Do we ever see the mention of V2 other than for this purpose? I think not.
FlightPathOBN, what does not "compute"?
Moderator
Consider several things -
(a) AFM takeoff performance addresses both AEO and OEI, although the latter is the larger interest. Once the initial takeoff is over, the OEI climb becomes the concern.
(b) AEO, the main aim then should be to stay above the OEI calculated profile so that terrain clearance concerns are not a problem in the event of a failure during the initial climb
(c) for AEO in the case of turns, turn radius may/may not be critical on one/both sides of the splay - this should be made clear in the company's published procedures. If both are critical, then maintaining an arbitrarily higher than procedure-presumed speed OR a higher bank angle can compromise the procedure's design and, hence, terrain clearance. If the terrain problem is only on one side (typically the outside splay) then the higher bank angle may be OK but the higher speed not OK. The procedure should provide sufficient information for pilot guidance such that the pilot need only to fly as prescribed to address the basic concerns.
It really is just not on for the wider pilot community to have to second guess whatever it may have been than the procedure designer was thinking at the time ...
(d) in general, I would expect something along the lines of the following to be in vogue, depending on specific Type handling considerations -
(i) prop, AEO, fly the OEI body angle, or a little higher, subject to turn radius considerations.
(ii) jet, AEO, fly the prescribed body angle, which will give a predictable speed somewhat above V2. Generally, V2 is considerably lower than the best climb speed - it becomes a juggling act to pick a middle ground speed which takes advantage of this but doesn't penalise the takeoff by requiring a specific acceleration to achieve an above V2 speed. Typically, jets look to something around V2+10 to V2+20 as a useful target AEO.
Generally, and especially for the higher performance twinjets, maintaining V2 AEO requires too high a body angle for passenger comfort (read panic) and may impose a significant pilot workload in the event of engine failure from the point of establishing the appropriate OEI numbers - it can be very easy to find oneself well below V2 after the pushing, pulling, and swearing has settled down. Far better, perhaps, to be somewhat closer to the OEI body angle when the noise stops ?
(e) Vx/Vy are pertinent to small GA Types but are not typically a driver in heavy aircraft.
Some specific comments -
do not retract flap until turn complete
emphasis is on speed control for radius control and, secondarily, climb gradient considerations
then a higher speed may be specified. If required, this should be in the procedure
it must be in the procedure otherwise the calculated splays can be totally compromised. With turns, both speed and bank angle become critical.
(a) AFM takeoff performance addresses both AEO and OEI, although the latter is the larger interest. Once the initial takeoff is over, the OEI climb becomes the concern.
(b) AEO, the main aim then should be to stay above the OEI calculated profile so that terrain clearance concerns are not a problem in the event of a failure during the initial climb
(c) for AEO in the case of turns, turn radius may/may not be critical on one/both sides of the splay - this should be made clear in the company's published procedures. If both are critical, then maintaining an arbitrarily higher than procedure-presumed speed OR a higher bank angle can compromise the procedure's design and, hence, terrain clearance. If the terrain problem is only on one side (typically the outside splay) then the higher bank angle may be OK but the higher speed not OK. The procedure should provide sufficient information for pilot guidance such that the pilot need only to fly as prescribed to address the basic concerns.
It really is just not on for the wider pilot community to have to second guess whatever it may have been than the procedure designer was thinking at the time ...
(d) in general, I would expect something along the lines of the following to be in vogue, depending on specific Type handling considerations -
(i) prop, AEO, fly the OEI body angle, or a little higher, subject to turn radius considerations.
(ii) jet, AEO, fly the prescribed body angle, which will give a predictable speed somewhat above V2. Generally, V2 is considerably lower than the best climb speed - it becomes a juggling act to pick a middle ground speed which takes advantage of this but doesn't penalise the takeoff by requiring a specific acceleration to achieve an above V2 speed. Typically, jets look to something around V2+10 to V2+20 as a useful target AEO.
Generally, and especially for the higher performance twinjets, maintaining V2 AEO requires too high a body angle for passenger comfort (read panic) and may impose a significant pilot workload in the event of engine failure from the point of establishing the appropriate OEI numbers - it can be very easy to find oneself well below V2 after the pushing, pulling, and swearing has settled down. Far better, perhaps, to be somewhat closer to the OEI body angle when the noise stops ?
(e) Vx/Vy are pertinent to small GA Types but are not typically a driver in heavy aircraft.
Some specific comments -
do not retract flap until turn complete
emphasis is on speed control for radius control and, secondarily, climb gradient considerations
then a higher speed may be specified. If required, this should be in the procedure
it must be in the procedure otherwise the calculated splays can be totally compromised. With turns, both speed and bank angle become critical.
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well, pistinaround mentioned the Vy is just 5 kts to max 15 kts above V2 on that turboprop. Also, you will never be at V2 AEO unless you SLOW down to V2. Certification is such that your VR will provide V2 at 35ft OEI. If you rotate at VR AEO you will be higher than V2, unless you pitch high up to bring your speed back to V2 while turning 30 degrees. isnt it?
