As you may have already figured out, there are many factors to consider.

Directly from the Airbus procedure:
-At takeoff
-If before V1
The takeoff should be rejected only if significant airspeed variations occur below indicated V1 and the pilot decides that there is sufficient runway remaining to stop the airplane
-If after V1
Call- “Windshear TOGA”
-Thrust Levers TOGA
-Reaching VR ROTATE
-SRS Orders FOLLOW

The reality is in most cases the V1 and VR speeds are higher than Vmu (Mininmum Unstick) as they are usually optimized for second segment climb performance. Put simply, the airplane will fly at speeds lower than V1 and Vr.

The only other factor that I consider is the calculated distance remaining after a reject is performed at V1- depending on the runway (say a 12,000' runway) I've seen as much as 3,000' feet remaining. As the Airbus procedure says, if you 'believe' that it is possible to stop, then stop. If you do not believe you will stop (e.g. KLGA) then GO!!

 

You are absolutely right about Vmu and its relation to V1 and Vr. However, from what you posted, it looks like you must be below V1 to even consider aborting. There is no mention of aborting in the "If after v1" section. It only lists it as a possibility in the "If before V1" section. So after v1, according to the procedure above, your beliefs don't enter into the discussion.... you just go. by:

-If after V1
Call- “Windshear TOGA”
-Thrust Levers TOGA
-Reaching VR ROTATE
-SRS Orders FOLLOW

 

No sir, you are wrong. Here is your Q3. Enjoy!

Sarcasm...

Two of my military airplanes didn't have refusal speeds. They had regular V1, VR, V2 speeds.

-Fatty

 

Why would you crash if you didn't make Vr ?

In some cases V1=Vr. In any case, Vr is 1.05 X Vmca. Then, once airborne, V2 is 1.10 X Vmca.

BTW, this stuff is very well covered in the Euro ATPL theory exam if you ever get a chance to view the books.

There's a lot of margin in these V speeds!

I've taken off hundreds of times where, had I gone OEI, my reaching the 35ft screen height at V2 was not assured and I knew it. Even so, takeoff is still legal!


If you abort after V1, you better have a good lawyer, if you're still alive!

If you reach V1, keep going.


AL

 

Completely off topic, while dead heading on the Boston shuttle Tuesday, a lady sitting next to me commented on the fact that she had been involved in three airlline accidents and a flight where a baby had been delivered. Specifically, one such incredible disaster happened when the airplane got airborne, encountered windshear, and then the pilots brought it back down and over ran the runway, broke up and burned. She exited via the overwing exits. Did I mention that she also looked like she owned 100 cats?

I just had a DA moment ... hahaha. reference 4m 34s YouTube - Lt. Napoleon

-Fatty

 

The primary concern with V1 and Vr is not second segment climb!
In most cases, you're only assured the screen height of 35ft at V2.
V1 is predicated on Vmbe and Vmcg. Vr may be equal to V1 but it's always greater than Vmu!



AL

 

Deez340,

What I showed there is what Airbus says and I find it a very useful guideline.

My personal thoughts I wrote at the end; i.e. if there is lots of ASDR it may be worth considering an abort. Therefore, most times I would be go oriented after V1. I've seen a sim demonstration of what even a 10 kts tailwind will do if an abort is performed from V1 and it was not pretty. You might stop it in time if you tried, but it's more likely the airplane will fly if you elected to go.

 

alvrb211,

Maybe I wasn't clear before, as I understand how and why the V speeds are done. However, with sufficient runway, the speeds are usually higher than the minimum required (to get off the ground) to allow the aircraft to accelerate to higher speeds on the ground to have better climb performance once airborne. i.e. for a given aircraft of the same config, weight and field conditions, the speeds will be higher for a longer runway than for a shorter one. My point was that sometimes a go decision is still best below V1 as the airplane is still quite capable of flying.

I've seen V speeds of (approx) 166, 170, 172 for a heavy A321 using Config 1on a long runway. If I encountered windshear at say 160 KIAS, depending on severity I am inclined to go TOGA and take it in the air. That bird does not stop well when heavy.

 

You have to beware of Vmcg if you're below V1

AL

 

Strange post don't you think?

Not sure why you use the "professor" moniker. This is basic stuff.

I'm not European. Why the reference? Do you fly with a lot of Europeans who, in your view, talk-a-big-game-but-can't-fly-for-crap, as you put it?

That's a pretty racist and bold statement. I'd feel just a little stupid after posting something like that on a public forum!

I'm not sure what nationality you are. Perhaps you don't like or respect Europeans, or European pilots, in general.

What "in your view" constitutes "talking a big game" or "being unable to fly for crap"?

AL