V2 and the 4 segment climb

[Polar742]

That all depends GREATLY on the aircraft being flown. Some have VR and V2 relatively close that there is no way to properly get the aircraft off the ground without yanking it off at VR. Some aircraft climb at V2 at the same pitch attitude with all or OEI (the Dash 8) for example.

Just, for the love of Alla people, don't accept the VMC climb if your weight is above the max weight for your runway performance, it is illegal as hell.

To expound on that, if you have "improved climb" performance numbers, you will probably be past V2, even in an OEI situation.

With Vr moved closer to V2, it allows the aircraft to gain more energy for a OEI climb scenario. In this scenario, for example, you might have a V1 of 151 Vr of 162 and V2 of 167, where in a normal scenario for that weight you might see a V1 of 151, Vr of 156 and a V2 of 167.

No matter how you company manipulates the derived numbers (V1, Vr) V2 should be a constant at a given weight and flap setting.

 

[Polar742]

Unless we are really heavy, one engine out isn't really that bad. We get two out and things get interesting really quick.

<snip from takeoff briefing>

If we lose one, we'll continue out, go work the problem. We'll have to dump gas then come back and land. If we lose two, start dumping gas...."

</snip>

 

[seagull]

No matter how you company manipulates the derived numbers (V1, Vr) V2 should be a constant at a given weight and flap setting.

No, actually. V1 will move based on runway available and condition. For us, all data is predicated in V1max, as long as the accelerate-stop distance yields at least 3000' remaining runway length. If that is not possible, we start reducing V1 to maintain 3000' runway remaining, until we hit V1min. At that point, you will eventually reach a balanced field length.

 

[Polar742]

No, actually. V1 will move based on runway available and condition. For us, all data is predicated in V1max, as long as the accelerate-stop distance yields at least 3000' remaining runway length. If that is not possible, we start reducing V1 to maintain 3000' runway remaining, until we hit V1min. At that point, you will eventually reach a balanced field length.

That's what I meant to convey. Obviously, I didn't get that goal. The main point was that V2, no matter what adjustments are made to V1, is constant.

I did not know about the V1 max and the 3000' remaining. Here, it seems that our V1s match up very closely to what the FMC calculates. Vr seems to be the manipulated number here.

 

[Bandit_Driver]

<snip from takeoff briefing>

If we lose one, we'll continue out, go work the problem. We'll have to dump gas then come back and land. If we lose two, start dumping gas...."

</snip>

Yep sounds pretty familiar. Hopefully if anyone ever loses two the flaps and gear are already up or you still have eng 1 or 2 turning.

 

[dasleben]

Oh, you guys and your 3-4 engines. So spoiled.

 

[MikeD]

Oh, you guys and your 3-4 engines. So spoiled.

You got nuthin on the BUFF.....

 

[dasleben]

You got nuthin on the BUFF.....

8 APUs?

 

[seagull]

That's what I meant to convey. Obviously, I didn't get that goal. The main point was that V2, no matter what adjustments are made to V1, is constant.

I did not know about the V1 max and the 3000' remaining. Here, it seems that our V1s match up very closely to what the FMC calculates. Vr seems to be the manipulated number here.

The 3000 is a company thing, just adds an extra margin.

Actually, also, depending on the V1 factor, you could have a different V2, as the amount of flaps would vary depending on the limitation, which would move the V2 with it.

Vr should not move much relative to V2, I wouldn't think.

 

[BobDDuck]

Vr should not move much relative to V2, I wouldn't think.

Our Vr changes (relative to V2) during windshear conditions. We'll use the max runway takeoff weight for our Vr but use the correct V1 and V2 for our weight. Obviously, Vr isn't going to move up enough to get above V2 but sometimes if you are super light your MRTW Vr is closer to V2 than V1.

EDIT: Reading this thread and some of the other ones posted recently I realized just how little I really know about speeds and what not and how they all mesh together.

 

[Bandit_Driver]

You got nuthin on the BUFF.....

Ahh you guys and the dreaded 7 engine takeoffs...

 

[seagull]

Our Vr changes (relative to V2) during windshear conditions. We'll use the max runway takeoff weight for our Vr but use the correct V1 and V2 for our weight. Obviously, Vr isn't going to move up enough to get above V2 but sometimes if you are super light your MRTW Vr is closer to V2 than V1.

EDIT: Reading this thread and some of the other ones posted recently I realized just how little I really know about speeds and what not and how they all mesh together.

That is not your Vr changing, per se, it is just artificially using a performance limited Vr.

 

[MikeD]

Ahh you guys and the dreaded 7 engine takeoffs...

Hey man, you should see how close to death those guys get when that critical engine is inop and they're riding the margin of Vmc!

 

[Polar742]

The 3000 is a company thing, just adds an extra margin.

Actually, also, depending on the V1 factor, you could have a different V2, as the amount of flaps would vary depending on the limitation, which would move the V2 with it.

Vr should not move much relative to V2, I wouldn't think.

I will agree that V2 does move with the flaps. However, Vr does move relative to V2 if we use improved climb. Why? I'm not sure. You're pretty much the guru, so I'll defer to any answer you give.

As far as I can tell, V2 only moves with weight and flaps. Vr seems to move based on either BFL, or unbalanced field or improved climb.

 

[Bandit_Driver]

Hey man, you should see how close to death those guys get when that critical engine is inop and they're riding the margin of Vmc!

How do they define the critical engine on the Buff?

How screwed are they on V1 cuts?

 

[MikeD]

How do they define the critical engine on the Buff?

How screwed are they on V1 cuts?

Good question. I'll have to ask a BUFF friend of mine, since now I want to know also.

For V1 cuts...abort they have a HUGE drag chute they can deploy. For the GO portion......I don't know. Thats ALOT of bombs to emergency jettison to lighten up.

 

[ppragman]

How do they define the critical engine on the Buff?

How screwed are they on V1 cuts?

Lol, "hey Mike, did we just lose an engine?!"

 

[SteveC]

...
For the GO portion......I don't know. Thats ALOT of bombs to emergency jettison to lighten up.

Remind me not to buy a house within 5 miles of the end of one of their runways.

 

[MikeD]

Remind me not to buy a house within 5 miles of the end of one of their runways.

It amazes me that people live around Air Force Bases or Air Stations, especially off the extended runway centerlines. There's a reason these places started life out on the middle of nowhere. When I had my engine failure on takeoff in the Hog, I couldnt get rid of my munitions for this very reason and had to struggle to keep the jet airborne. Although if the jet is going to crash anyway, it might not make a difference.........only geographically.

 

[Roger, Roger]

Lol, "hey Mike, did we just lose an engine?!"

Ah yes, the dreaded 7-engine approach...