V1 & V2 speeds

[johnm]

Be engine out aware too. Airline pilots are. Every takeoff has a consideration of aborted take off with rapid initiation for any failure before V1. If they get an uncontrollable fire things happen quickly too but it's all in the training and attitude to risk. Nev

.................. Just to get a better understanding of this - below V1 - an airline pilot can handle an engine out - they can stop on the strip or an overshoot area ?

 

Between V1 & V2 - its a metal tube that might plough the grouund ? - not good to have an engine out in this zone

 

At V2 you can fly away to safety (relative safety)

 

Thanks

 

 

[spacesailor]

The "Concord" flew V2 in France, with a punctured wing tank, well above V1 and no chance of stopping on the ground safely or not safe.

 

We all read the aftermath of that

 

spacesailor

 

 

[Roundsounds]

This may be overly simplifying the situation, but basically appropriately certified aircraft:

 

- Before V1 - you can stop within the available runway

 

- At V1 - you can continue the takeoff and climb away

 

Typical examples of these types are all RPT and IFR charter aeroplanes.

 

 

[Roundsounds]

Go to section 15, page 16 (labelled 15-16)

 

http://www.faa.gov/regulations_policies/handbooks_manuals/aircraft/airplane_handbook/media/faa-h-8083-3a-6of7.pdf

 

 

[ian00798]

The "Concord" flew V2 in France, with a punctured wing tank, well above V1 and no chance of stopping on the ground safely or not safe.We all read the aftermath of that

spacesailor

Ultimately v2 is just another speed. The idea that you can climb away safely following loss of an engine requires certain assumptions, ie remaining engines producing maximum, or near maximum thrust, gear up and aircraft cleaned up as much as possible. None of these are true in the case of Concorde, it had one engine shut down, another one not producing significant power, and the gear was stuck down. Not to mention the fire probably wasn't making positive aerodynamic contributions.

 

Ultimately, the crew that day did the best they could with the hand they were dealt, there wasn't really anything that could have saved them that day. We can really only speculate what would have happened had they chose to abort on the runway, but they were a certainty to overrun the runway and given the massive fire already in progress I don't imagine that going too well either.

 

 

[Birdseye]

- At V1 - you can continue the takeoff and climb away

Not correct, exceeding V1 just means that you probably cannot abort and stop in the available runway. You still have to achieve flying speed and minimum control speed (if asymmetric) to safely continue in flight.

 

 

[Roundsounds]

Not correct, exceeding V1 just means that you probably cannot abort and stop in the available runway. You still have to achieve flying speed and minimum control speed (if asymmetric) to safely continue in flight.

"Not correct", really? When you say minimum control speed, I assume you mean VMCA as V1 has already taken VMCG into consideration. In fact the larger aeroplanes minimum V1 is often driven by VMCG.

To quote the FAA definition:

 

"V 1 —Critical engine failure speed or decision speed. Engine failure below this speed should result in an aborted takeoff; above this speed the takeoff run should be continued."

 

What part of "continue the take-off and climb away" do you consider incorrect? I would consider continuing the takeoff to include:

 

- acceleration

 

- keeping the aeroplane on the runway to achieve VR

 

- rotation at the correct rate to the appropriate target attitude

 

- achieve / maintain V2 - V2+5, retract the landing gear

 

- follow the prescribed one engine inoperative cleanup procedure

 

- perform the engine malfunction procedure at an appropriate time during / after the cleanup baaed upon the nature of the failure.

 

To answer Johnm's question of what happens between V1 and V2, see above dot points and no there is no phase whereby the aeroplane becomes "a metal tube that might plough into the ground". This assumption is based upon a single engine failure with all other systems operating normally.

 

 

[johnm]

...... plough the ground Roundsounds (not plough into it) - a farmer ploughs / furrows the ground

 

V1 is a decision speed - go or stop

 

V2 is fly away safely

 

Between V1 & V2 (assuming they are different speeds ?) you are going back to the ground

 

Correct or wrong ??????????

 

 

[dutchroll]

.................. Just to get a better understanding of this - below V1 - an airline pilot can handle an engine out - they can stop on the strip or an overshoot area ?Between V1 & V2 - its a metal tube that might plough the grouund ? - not good to have an engine out in this zone

 

At V2 you can fly away to safety (relative safety)

 

Thanks

V1 is the speed below which, after an engine failure, the takeoff can be rejected and the aircraft will stop on the remaining runway. It takes into account the partial loss of stopping systems (reverse thrust, etc) when an engine fails. Above V1, the takeoff must be continued. V1 speeds are based on environmental data, runway available, takeoff weight, etc. V1 speed is slightly conservative. Eg, the loss of an engine results in reverse thrust only being available from one engine, so in the V1 calculation, no reverse thrust is used.

There is no significance of the region between V1 and V2, except that somewhere between those speeds the aircraft will reach VR (rotate speed) on its remaining engine/s and takeoff from the remaining runway.

 

V2 is the speed at which the aircraft is initially established in the climb after an engine failure, with the landing gear retracted. It is the speed designed to achieve a margin above stall and minimum control speeds while achieving the initial obstacle clearance/climb gradient with an engine failure. It is flown to a very tight tolerance until the aircraft reaches its "acceleration altitude", which for us is 1,500ft above the runway elevation.

 

At acceleration altitude, pitch angle is reduced to attain a level segment or a very shallow climb and the aircraft is accelerated through its flap retraction speeds and completely cleaned up.

 

The most critical time to have an engine failure is right at V1. There is no longer sufficient runway to stop, but you have just lost half your thrust and so acceleration to rotate speed is slow. Plus you need to maintain directional control with one engine failed and one engine going flat out. There is not much runway left when those main wheels finally leave the ground after what seems like an eternity! At heavy weights at least. At lighter weights, acceleration after losing an engine at V1 is better and runway remaining to get off the ground is not quite so much a problem. The aircraft is pitched appropriately to achieve V2 speed while climbing out and the gear is retracting (that's about 10 degrees nose up for my aircraft, whereas normal pitch after takeoff is at least 15 degrees). At no point are you supposed to die during this phase, but there's not much room for error.

 

 

[Birdseye]

"What part of "continue the take-off and climb away" do you consider incorrect? .

Just as I have already said, attaining V1 does not guarantee that a takeoff will be successful and the aircraft will climb away safely. It is merely a go/no go speed.

 

 

[Roundsounds]

Just as I have already said, attaining V1 does not guarantee that a takeoff will be successful and the aircraft will climb away safely. It is merely a go/no go speed.

Under what circumstances would an aircraft such as a B737 or A330 not make a successful takeoff and climb out (using manufacturer / operator approved procedures) having had an engine failure at/after V1?

 

 

[Nobody]

Under what circumstances would an aircraft such as a B737 or A330 not make a successful takeoff and climb out (using manufacturer / operator approved procedures) having had an engine failure at/after V1?

A second engine failure?

 

 

[kasper]

Gee i'm glad i fly simple stuff ... the slow weightshift wing for the trike only has 1 speed - 50mph flight - take off, climb, crusie and decent are all at 50 ... so instead of V1 etc I have 1 V.

 

 

[dutchroll]

Again in pure practical terms for the non commercial pilot , without haggling over definitions:

 

There is no circumstance which would result in a crash provided:

 

1) If the engine failure happens prior to V1, the takeoff is aborted

 

2) If the engine failure happens at or after V1, the takeoff is continued on the remaining engine.

 

All of the above assumes the aircraft is competently handled when the engine fails and the correct techniques are followed. The calculation of takeoff performance data guarantees that the aircraft will stop in the remaining runway, or fly away off the remaining runway given these circumstances.

 

V1 - a speed on the runway at which your decision in the event of an engine failure fundamentally changes (stop versus keep going).

 

V2 - a speed in the air at which, with an engine out, you get the best possible initial climb performance without losing control of the plane.

 

 

[johnm]

'At no point are you supposed to die during this phase, but there's not much room for error' - well put

 

Sorry Dutch - for those with lower smarts ................ theoretically:

 

- can there be a difference between V1 & V2 - is (or could there be with some aircraft) there a 'zone' between the 2 - or is it, when you get to V1, you are guaranteed to get to V2

 

 

[dutchroll]

'At no point are you supposed to die during this phase, but there's not much room for error' - well putSorry Dutch - for those with lower smarts ................ theoretically:

 

- can there be a difference between V1 & V2 - is (or could there be with some aircraft) there a 'zone' between the 2 - or is it, when you get to V1, you are guaranteed to get to V2

There is always a difference between the two speeds because V1 is always a speed which is achieved on the runway and V2 is always a speed which is achieved once airborne. That's the nature of the way they're calculated.

You will always achieve V2 if you get the plane airborne off the runway available. However, whether you get the plane off the runway depends on whether you made the correct decision when the engine failed!

 

The only two speeds which can, in some circumstances, actually be numerically the same, are V1 and VR (decision speed, and rotate speed). As soon as those wheels leave the ground, V1 is irrelevant. So for example, if V1 and VR were the same speed, all it means is that you've got enough runway to reject the takeoff right up until you pull back on the stick and get airborne. Once you're airborne, you're continuing. We don't try to land back on the runway after an engine failure. If you get into the air with the loss of an engine, you can always fly away. That's how commercial jets are designed.

 

 

[djpacro]

Not all twins have performance data provided for rejected takeoff and continued takeoff. The POH for at least one twin has a statement to the effect that regardless of the above ... do not continue on one engine.

 

 

[dutchroll]

Disclaimer: Yes what Dave says is very true. These V speeds are often not relevant to smaller twins in the GA world.

 

 

[Guest Howard Hughes]

This may be overly simplifying the situation, but basically appropriately certified aircraft:- Before V1 - you can stop within the available runway

- At V1 - you can continue the takeoff and climb away

 

Typical examples of these types are all RPT and IFR charter aeroplanes.

The requirement for a balanced field is based on the aircraft's weight and certification standard, not its category of operations. Chieftains (for example) are able to fly both RPT and Charter and are not required to comply with balanced field requirements.With regard to the go, or no go decision, at V1 you ARE going, anything below that you can safely abort. During the certification process, a two second pause is used at V1 to allow for the recognition/decision making process before braking is applied.

 

Reverse thrust is not used in the calculation of stopping distance from a V1 abort, nor a landing calculation, it is maximum braking only.

 

 

[Yenn]

Even if you get to V2 there is no guarantee about flying. A friend of mine lost a push-pull Cessna, by trying to retract the wheels at low altitude. That results in a massive sink rate. Not pretty.

 

 

[Roundsounds]

Even if you get to V2 there is no guarantee about flying. A friend of mine lost a push-pull Cessna, by trying to retract the wheels at low altitude. That results in a massive sink rate. Not pretty.

I'm pretty sure this topic is about aircraft fitting into CAO 20.7.1B (larger multi-engine turbine powered aeroplanes)

 

I don't think a Cessna 337 falls into that category?

 

 

[Roundsounds]

Reverse thrust is not used in the calculation of stopping distance from a V1 abort, nor a landing calculation, it is maximum braking only.

Yes, but if thrust reversers aren't available there's a penalty. We could go on for days going into the nitty gritty, why I suggested a simplified lay and version of the requirements.

 

 

[dutchroll]

My assumption, when things like "V1" and "V2" are mentioned is that it really refers to heavier certified aircraft. Not twin Cessnas, Barons, etc which don't use this type of performance data.

 

If you have an engine failure at or above V1 in a commercial jet, you will get airborne and you will reach V2, barring any mishandling of the aircraft. The performance data will prohibit you taking off at weights or in environmental conditions which preclude that.

 

 

[ian00798]

This thread is just really making me dread doing ATPL theory, it just sounds really complex. So many ifs, buts maybes and grey areas in general.

 

 

[dutchroll]

This thread is just really making me dread doing ATPL theory, it just sounds really complex. So many ifs, buts maybes and grey areas in general.

Oh we haven't even got into the segmented climb yet!