V1, Vr and V2 question

[scubabri]

I'm having a tough time understanding the relationship between V1, Vr and V2 and accl-stop/accl-go

The way I understand it for the aircraft I am currently in (BE90 right seat) is that:

V1=Vr this is based on the accl-stop speed based on performance charts taking into consideration weight, DA and rwy conditions

V2= the speed that you reach at 35' over the end of the runway, but I am still not understanding why/how this is important and how/why it's different than Vyse

accl-stop= the distance where you can accl up to V1/VR and still stop with enough rwy as to not crash into the GS antenna.

accl-go= this is what I am not quite clear on. Lets use 2 examples here 10,000' rwy and a 3600' rwy.


At or before V1/VR on either rwy, it's a no brainer, stop the aircraft.

After V1/VR on a 10'000, If I had an engine failure, I could still put the aircraft down, and have lots of room to spare, or if I am out of rwy, I should be at a speed that I could continue my climb at Vyse

After V1/Vr on a 3600' rwy, I have an engine failure, my only option is to continue the take-off, but I am not clear why the accl-go calculation is important, there is not much I can do about it, so I continue my climb at Vyse

So what am I missing here?

b

 

[JHook]

accl-stop= the distance where you can accl up to V1/VR and still stop with enough rwy as to not crash into the GS antenna.

You'd have to have some pretty serious directional control issues to hit the GS antenna.

 

[172driver]

V1 is takeoff decision speed. Eng fails before V1, you abort. After V1, you continue the takeoff.

Vr is usually higher than V1 and is obviously rotation speed.

V2 is basically Vyse in the takeoff configuration. You must be able to reach V2 by 35' over the threshold and, using the appropriate departure procedure, be able to clear obstacles.

Accel-stop you got pretty well.

Accel-go is the length the rwy must be in order for you to lose an engine at V1, continue the takeoff, and reach V2 by 35' over the threshold. Obviously, your acceleration is slowed by the loss of an engine between V1 and V2.

The accel-go calculation is important because you will not be able to depart under 121 (and 135?) if you are unable to safely continue the t/o and climbout with an eng failure at V1.

In your 3600' rwy example, let's say accel-go is 5000'. You will smash into the trees, app. lts, etc. at the end of the rwy because it would take you 5000' to climb to 35' AGL at the end of the rwy. Not good, regardless of the regs.

After V1/VR on a 10'000, If I had an engine failure, I could still put the aircraft down, and have lots of room to spare,

Nope. After V1, if you abort, there will not be enough rwy left to stop.

BTW, when accel-stop and accel-go are the same, you have a balanced field.

 

[350DRIVER]

Nope. After V1, if you abort, there will not be enough rwy left to stop.

You are kidding right.? ( I hope) A king Air 90 with 10,000ft of runway. hmmm You could easily go past V1 then abort and have plenty of runway left out of the 10,000.

All depends on equipment, runway, conditions, temps, etc,


3 5 0

 

[2000flyer]

Vr is usually higher than V1 and is obviously rotation speed.

Vr is ALWAYS equal to or higher than V1, not usually. Why would you reach rotation speed before you've reached your take-off decision speed?

2000Flyer

 

[SkyWestCRJPilot]

An acquantance told me when he flew twin otters on floats in Alaska that Vr was lower than V1. They would take off (rotate) in ground effect over the water, then wait for V1 before climbing out of ground effect. It's the only time I've ever heard of Vr before V1.

In the case of taking off a runway with plenty of room to stop, in that case V1 equals Vr. You wouldn't want to abort after you are airborne even if you had plenty of runway available. It is generally believed that for most multiengine turbine airplanes that once you have rotated and you lose and engine it is safer to deal with the emergency in the air than on the runway travelling at high speed. (at least that's how it is in the EMB-120 and CRJ)

 

[Freight Dog]

Hey Fly_Chicaga... congrats on getting hired. Where did you get hired?

 

[SDdriver]

Everyone pretty much seems to have covered this pretty good. THe only thing that i would like to add is, don't get so caught up in procedures and regs, and become so automated as to forget about commen sense altogether.

using the example of the C90 on a 10k rwy. If you lost that engine at V1 would you really continue with 7k of rwy in front of you? COme on, it would be much safer just to pull the good one back and settle back on the rwy. Use good judgement but think about commen sense also. I mean taking off on a 3600ft and 10000ft rwy you should be thinking about that ahead of time anyway. My opinion is that a pilot shouldn't get so caught up into the procedures and regs as to lose his commen sense. There are circumstances that those procedures and regs will kill you not save you. THink about it.

SD

 

[enigma]

Just a few quick thoughts. First, to my knowledge, a Kingaire is not certified to utilize V1. It is a Vr, V2 airplane, so to try and explain v1, vr and v2 properly, you need to pick an example that is truly a v1 airplane.

Some responded with the opinion that you would be ill advised to continue the take off in the example given. Maybe so, but remember that the Kingaire in question is not a v1 airplane. In a true v1 aircraft, you really don't want to abort above v1. There are numerous factors relating to this fact. I'm short on time and don't have time to get into all of them, but one example could be brake energy. You see, the brakes can only dispate just so much heat, and a high speed abort could possibly possess more energy than the brakes have the ability to deal with. You could find yourself with no brakes and not be able to stop even if you had 10000ft.

If the issue hasn't been cleared up by tommorrow, I'll try and jump back in with more info.

regards,
enigma

 

[antney]

flychicago nice pic on your avator, are you promoting the 170 at express. also can you send me the lin k for that, looks pretty good, would like to put it in the crew lounge and blow it up and place it next to our RJ Donation box. Anyways looking forward to seeing you online, goodluck the reset of the way through training, hope Vic is teaching you a lot.
Anthony