V1 Rotate

[DC8 Flyer]

My operator uses power, and we have 4 thrust producing thingys out there.

 

[TonyC]

No jet takeoffs are a max "power". Power is for props. Jets use thrust.

And yes, most takeoffs are done at "reduced", "flex", or "alternate" thrust settings. If the runway can be balanced and the aircraft meet second-segment climb requirements, using reduced thrust reduces wear on the engines.

We set "Standard Power" or "Max Power" with the throttles/thrust levers. I wonder how we ever get airborne.





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[satpak77]

good points

Pre-V1 is not the only factor in an abort decision. There are high-speed and low-speed aborts. Usually 121 carriers consider anything above 80 or 100 KTS a high speed abort and do not recommend aborting after this speed unless the captain feels flight is not possible. In my company the captain makes the decision to abort. After 80 or 100 KTS (lower than V1) it is considered safer to continue on and have the full length of the runway to stop, even though performance figures allow it. Keep in mind your aircraft is still producing thrust and accelerating even with an engine failure and a high speed abort is more likely to cause tire blow-outs, brake overheating, etc.

also note the schoolhouse teaches "any light before V-1, abort" however if I am at Max weight, hot, high, with a legal runway length but a little shorter than desired, I will not abort on a yellow in the B-350. Many things can trip a yellow light, to include BATT CHARGE, RVS NOT READY, amongst other things. As I speed down a difficult runway, max weight, and my BATT CHARGE light blinks on, thus tripping the yellow warning flashers, 1 knot below V-1, I am not aborting, believe me. I am not rolling the dice on my tires and brakes and momentum and "real world" factors and trying to stop on the runway. I will rotate, assess the yellow light issue, and land.

Long runways or light load, etc, and I abort on all lights.

 

[Lead Sled]

It seems that, as with most things associated with aviation, there is some room for at least a little discussion. It seems that the definition of V1 is based on geographical considerations. There is the FAA definition and the JAA definition and they are very different.

Thanks to the miracle of "cut & paste", I've inserted the definition of V1 as contained in Part 1 of the FARs (OK, I know that they are now known as 14 CFR...):

V1 means the maximum speed in the takeoff at which the pilot must take the first action (e.g., apply brakes, reduce thrust, deploy speed brakes) to stop the airplane within the accelerate-stop distance. V1 also means the minimum speed in the takeoff, following a failure of the critical engine at VEF, at which the pilot can continue the takeoff and achieve the required height above the takeoff surface within the takeoff distance.

The point is that if V1 is the maximum speed in the takeoff at which the pilot must take the first action (e.g., apply brakes, reduce thrust, deploy speed brakes) to stop the airplane within the accelerate-stop distance, then the decision to abort or continue the takeoff must be made at some point prior to reaching V1 in order to allow for pilot reaction time.

For the rest of the world, the JAA definition is very simple: "V1 - Takeoff decision speed"

The actual calculation however, in terms of Accelerate-Stop distance (JAR 25.109), is that the aircraft may: "...continue acceleration for 2 seconds after V1 is reached with all engines operating (and) come to a full stop from the point reached at the end of that acceleration assuming that the pilot does not apply any means of retarding the aeroplane until that point is reached."

So under JAR a two second gap is permitted on reaching V1 before the pilot does anything, to allow for the decision to be made. The continued acceleration of the aircraft from that point is also allowed for, with both engines operating, for 2 seconds (a long time in aviation).

We're talking more than semantics here. By regulation, U.S. pilots, flying U.S. registered aircraft are required to comply with the MORE restrictive of either the FARs or the local regulations, if they are operating outside of domestic U.S. aiarspace. I think that it could be argued that the FAA definition is more restrictive, hence this is the one that I am compelled to use.

There are some other pertenant speeds as well...

VLOF is merely the speed at which the airplane becomes airborne. As far as the flightcrew goes, it's not even "part of the takeoff equasion". In other words, it just happens.

What the flightcrews do call is VR. When the "Rotate" call is made the PF (pilot flying) simply raises the nose. The airplane will liftoff when it achieves a sufficient angle of attack.

V2 (Takeoff Safety Speed) is the speed that you will have at 35' agl - in the event of an engine failure at or before V1. You maintain that speed until you have 400' agl and are clear of any immediate obstacles. (However, if you manange to have a speed faster that V2 you wouldn't want to allow it to bleed off - would would maintain whatever you had.) Once you are clear of the obstacles you enter the 3rd segment or acceleration phase of the where the aircraft is allowed to accelerate Vfto or Final Segment Takeoff Speed. As the aircraft is accelerating it is cleaned up appropriately as the various speeds are achieved. Under normal operations (all engines operating) V2 is of little interest to the crew - the airplane is acelerating like the proverbial "raped ape" - and it blows through V2 in very short order.

Sled

 

[Occam's Razor]

We set "Standard Power" or "Max Power" with the throttles/thrust levers. I wonder how we ever get airborne.





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Geez...I don't know. What static POWER rating do your engines have?

When you land your big jet...do you use the POWER reversers to help you stop?

 

[TonyC]

Geez...I don't know. What static POWER rating do your engines have?

When you land your big jet...do you use the POWER reversers to help you stop?

Hey, I thought you were in an indulging mood!





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