V2 Climb question

[pistinaround]

Iam a F/O on a regonal turbo prop and I have a question regarding a climb after departure from one of our ports.

Our company escape procedure states. For runway 18

" at 600 ft turn right onto heading 360 do not retract flap until turn complete intercept the 300 radial climb to MSA"

The airport is surrounded by high terrain to the south and a departure from runway 36 not always avaliable.

My question is should one climb at V2 to the acceleration altitude or climb at best rate or angle ?

Most Captains choose to fly at V2 but there is one in particular that flies it at Vy stating that if you climb at V2 and lose an engine you will lose to much energy and drop below your V2 climb speed this is why he chooses to fly at the faster speed.

My thoughts are you should climb at V2 as this is what the perfomance information is calculated on particularly the turn.

Any thoughts ?

[shock-absorber1]

How far are the V2 and the Vy usually on your aircraft?

[pistinaround]

Usually around 5 kts and at the most extreme cases about 15 kts

[Kelly Hopper]

If it is the escape path then the assumption is that you have already lost an engine. How many engines do you have on this turboprop?
Assuming it is two and you have lost one then V2 would be correct.

[stormyweathers]

Although your post was not absolutely clear at first, I see what your question is. It is my belief that the captain who flies at Vy instead of V2 on a normal departure with no failures to acceleration altitude is CORRECT. Your philosophy is that since engine out is based on V2, you should maintain V2 on every normal take-off until you have reached your normal acceleration altitude, just in case you do have an engine failure, and have to revert to the engine out procedure. His explanation is also logical.

[safetypee]

For Eu Ops – CS 25/FAR25 aircraft, the AFM climb performance is normally based on V2, thus fly V2.
However, if the turn requires an angle of bank greater than 15 deg, for a lower radius turn, then a higher speed may be specified. If required, this should be in the procedure; also check for any wind limits which might affect the assumed ground track.
If the engine failure occurs at a speed above V2, then maintaining that speed should give a better performance profile, but check the procedure detail and assumptions.
Also check, up to what point the engine failure is assumed after takeoff such that the procedure applies, i.e. after what point do you continue with a normal departure.

IMHO the Captain who flies a speed other than V2 is mistaken in his knowledge of aircraft performance and aerodynamics. Entering a turn at V2, the aircraft would be expected to fly at a lower attitude than for wings-level flight, thus adjust accordingly. If, in error, wings level attitude is maintained in a turn then speed will reduce; do not fly below V2.
Maintain V2 or the speed specified in the procedure.

[Wireless]

Vx would be perhaps be more suited than Vy if avoiding the nearby high terrain. It's slower too so the radius is tighter for the turn. I can see the logic of flying V2.

[Checkboard]

5-15 knots difference? I'd fly Vy as well.

[flyburg]

Sorry safetypee,

Couldn't disagree more! You follow the aom climbout procedure! Every takeoff has a escape maneuver, whether it be straightout or a turn! You follow the aom climbout profile. Should the engine fail before reaching v2 then you accelerate to v2, should the engine fail at v2 than you maintain v2 should the engine fail above v2 then you pitch up to decelerate to the speed given by the aom( usually anywhere between v2 and v2 +10) any speed above v2 on two engines gives you generally speaking beter climb performance than v2 so you clear the obstacles sooner.

So in answer to the initial poster, the one captain was right as long as the Vy was not above the recommended climbout profile speed you maintain to two engine acceleration height according to the aom.

If memory serves me right, on the fokker 50 you would pitch up to about 10 degrees which would give you about slightly more than v2+ 10, if the engine failed above this speed you would reduce speed to v2+10 if it failed between v2 and v2+10'you would maintain current speed!

[Dream Land]

I don't consider myself as an expert at performance, but I am in agreement with one of the previous posters, this procedure or escape maneuver is followed if you lose an engine after V1, in which case, V2 would be appropriate until reaching SE ACC altitude.

This maneuver is not to be followed when all engines are operating normally.

[safetypee]

flyburg,
I attempted to be as accurate as I could in my post; I referred to “… a better performance profile”, whereas you discuss “… better climb performance”, which I interpret as instantaneous climb gradient.
The obstacle clearance profiles are based on climb gradient with an engine failing at V1. An engine failure at any time after V1 puts the aircraft in a more advantageous ‘altitude’ position; but the crew do not know what the value of that is.
I agree with you; if below V2 accelerate to V2 and climb at V2, if above V2, say V2+10, then maintaining that speed should meet all of the initial performance requirements, but specific issues in company published emergency turn procedures should be checked.
With an engine failure above V2+10, the aircraft should similarly have an advantage, but without knowing the speed excess or altitude advantage gained so far, then the crew may wish to fly V2+10 or Vfto. My post might not have clarified these details.
However, harsh or rapid pitch manoeuvring should be avoided in order to achieve a slower speed, (cf DC10 Chicago accident), and in most circumstances a large speed reduction would not be required as such scenarios are more likely after commencing a normal departure route; then the aim is to meet the gradient requirement in that procedure. IIRC one of the normal departures from Lugano had several emergency climb break points, rerouting the normal departure to one of several alternative emergency engine-fail procedures with speed requirements.

[stormyweathers]

The original poster's question is simple. Do you fly at V2 on a normal take-off with 2 engines? Safetypee you say yes or no? If you say no than you agree with the captain who doesnt maintain V2.

[FE Hoppy]

Is the Vy for flaps extended or clean?

What does the TO guidance mode steer to with AEO. Many steer to V2+10 AEO and V2 to V2 +10 OEI.

Do you fly the "escape procedure" when AEO?

[VJW]

ETP's are suppose to be designed so that should you have an engine failure, you'd fly V2 - V2+20 until completion of the ETP and above MSA. Acceleration altitude is secondary when Terrain is a factor, so you only accelerate at the Minimum Flap Retract Altitude once clear of Terrain.

[FlightPathOBN]

Could the original poster explain the turn a bit further (degree of curve and bank angle)....and I am curious on the term 'escape procedure', if this is an EO departure, is the track close to the same as the AE departure track, or completely different? (many diverse departures have you climb to 400 and turn) Thanks.

[safetypee]

stormyweathers, you may not have interpreted the question in the same way which I have.
The question refers to an ‘escape’ procedure, which I relate to an emergency procedure with turn (ETP), it is only used with an engine failure (OEI); hence the reference to V2, etc.
If the question is for all engines (AEO) – a very unusual procedure, then the speed to be flown should be specified in the procedure. This speed will affect the obstacle clearance achieved, and if it is V2 then either a bank limit or a speed addition to maintain stall margin should also be specified for the turn.
More details required. See FE Hoppy #13 and FlightPathOBN #15

[pistinaround]

As the original poster I should have been more clear, we fly the escape procedure as a matter of course on every departure due to the terrain, (approx 5 miles from the Departure end of the runway) so in my example given the Captains in question are flying it AEO. The inital turn is conducted at 30 AoB AEO, and specifiecs 15 AoB OEI.
Thanks for the replies.

[FE Hoppy]

You're flying at V2 with 30° bank!

Hmm.

[FlightPathOBN]

You're flying at V2 with 30° bank!

That explains the 600. wow, this is certainly an e-ticket ride!

Not sure of the specifics, but I would look at getting the bank angle down, if the same track works with EO works at 15 degree bank angle, why the 30 AE?

It also may help to look at starting the turn at the min of 400, with less bank angle...even 15 EO is a stretch, and a lower turn start would give you some extra room, but there may be other reasons not readily apparent.

[stormyweathers]

No safetypee. I try never to interpret. The question REFERS to I quote: "...there is one particular captain...stating...if you climb at V2 AND LOSE AN ENGINE...you WILL lose too much energy...and DROP BELOW your V2 speed" Therefore he obviously still has his TWO engines. Now the poster wants to know whether that captain's explanation is valid?
If you're at V2 with all engines, and you suddenly lose an engine,(worst case right engine during a right turn) while in a 30 degree turn, you will lose serious lift. You will have to pitch down to recover the lost speed while decreasing the angle of bank to 15 degrees and regain V2. You will lose height as you pitch down to recover.
While with TWO ENGINES, speed is your friend, not your enemy. Use Vy while you can to increase your height. Also, at what angle of bank would you stall at V2? Assuming the right engine fails during a right turn, you might temporarily exceed the 30degrees that you are already in, before recognizing the failure and recovering and might exceed your stall angle...making things a real mess. I think the captain is right and has thought this through carefully.

[FlightPathOBN]

It would seem to me that if one lost a prop engine, a huge drag, in a 30 degree bank angle turn, you would need more speed than V2.

[safetypee]

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.

[westhawk]

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.

[FlightPathOBN]

In any case, V2 is a OEI speed,

Something does not compute...

[westhawk]

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.

[spud3]

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"?

[john_tullamarine]

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.

[stormyweathers]

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?