V1 is or is not a LOCATION on the runway...

[3WE]

if you have dragging brakes, lower thrust etc then your calculated v1 is not valid.

absolutely, 100% concur.

[3WE]

if you have dragging brakes, lower thrust etc then your calculated v1 is not valid.

Absolutely 100% concur...

BUT...

Put that in the context that the average big iron pilot does not really know if he's accelerating properly...

Put that in context of exactly what Gabriel says...you loose a chunk of headwind...

In that context, if you abort just before V1 you may NOT be able to stop .

So- 100% serious- V1 is a velocity. It is NOT a location on the runway.

However, the ability to stop safely IS RELATED TO YOUR location on the runway and your speed.

I do understand that V1 has a good 50+ year history as a method to know when to abort vs. continue.

But- the issue is that there may be some rare circumstances where it does not.

Final word here- You are offering up further discussion that I will study carefully- INCLUDING some methods of a speed/location check- so there may not be a huge disagreement here...

You don't have to agree with me- but watch out for that Gabriel dude

[BoeingBobby]

absolutely, 100% concur.

And you are both 100% absolutely WRONG! When you get to V1 you will still be at V1, it is just going to take you longer down the runway to get to it.

[BoeingBobby]

Put that in the context that the average big iron pilot does not really know if he's accelerating properly.

You don't think after flying the 74 for 15 years I can't tell when the aircraft is accelerating properly? Do you even realize the difference between ferrying an empty airplane vs one at max gross t.o. weight? I routinely will fly an empty aircraft to reposition it for a revenue flight. By the time I am at the end of a 10000' runway I am at 1500' climbing at 6000' a minute. I come out of HSV going to LUX in the -8 at 987000 lbs. 10000' runway, maybe 500' at about 800' minute. Now how are you going to put a marker on the runway and make that work? You would have to have some type of system to move it back and forth for every aircraft on every takeoff for the conditions of the aircraft and the MET.

[3WE]

Sorry 3WE and MCM.

Why on Earth do you want to do a speed vs position check to verify the actual acceleration matches the one of the take-off performance calculations when the plane is loaded with sensors?

I never said a speed vs position check THAT COULD ONLY BE DONE BY THE CREW VISUALLY CHECKING FOR A MARK/LANDMARK WITH ABSOLUTELY NO HELP FROM MODERN ELECTRONICS...

However, are you hearing a great explanation of V1's potential flaws other than, "it's what we've always done (including when you and I ride in the back) and we're still here posting on aviation forums."?

[Gabriel]

You don't think after flying the 74 for 15 years I can't tell when the aircraft is accelerating properly?

Of course you can.

In this accident, none of the 4 quite experienced pilots that were in the cockpit noted anything strange like a too slow acceleration. The investigation also revealed dozens of others similar incidents or accidents where the crew (of at least two pilots in each case) didn't realize either that there was something wrong until too late in the take-off roll, if ever.

But you are too good for that. It won't happen to you.

The problem is, to have 15 years flying the 74 there must have necessarily been a time where you had 1, 2 and 3 years flying it.

[Gabriel]

Gabriel, Flex is an Airbus term and has nothing to do with Boeing reduced thrust takeoff settings. I am not a "Bus" driver so I have no idea what it is. And TOGA is NOT always max thrust on takeoff. TOGA will give you what ever setting you have put in the FMS for the takeoff, be it a reduction or max. As far as the rest of this about runway markers for takeoff safety, YOU GUYS HAVE NO IDEA! IT WON'T WORK, NEVER WILL unless they start making runways as long as Edwards AFB.

Okay, the specific terminology differs between manufacturers and perhaps between operators too. But there are 2 very different types of reduced-thrust take-offs with the characteristics I described.

By the way, I first saw Flex in the MD-80. And I think that Airbus actually doesn't call it flex either.

[BoeingBobby]

Okay, the specific terminology differs between manufacturers and perhaps between operators too. But there are 2 very different types of reduced-thrust take-offs with the characteristics I described.

By the way, I first saw Flex in the MD-80. And I think that Airbus actually doesn't call it flex either.

Off the web.....

"FLEX" is the standard takeoff thrust setting used on Airbus aircraft, unless departing a contaminated (wet / icy) runway or if performance constraints (short runway or hot and high) exist, in which case TOGA (full thrust) is used.

"FLEX" takeoff settings use an assumed temperature thrust reduction to preserve engine wear and thereby prolong engine life.

[BoeingBobby]

Of course you can.

In this accident, none of the 4 quite experienced pilots that were in the cockpit noted anything strange like a too slow acceleration. The investigation also revealed dozens of others similar incidents or accidents where the crew (of at least two pilots in each case) didn't realize either that there was something wrong until too late in the take-off roll, if ever.

But you are too good for that. It won't happen to you.

The problem is, to have 15 years flying the 74 there must have necessarily been a time where you had 1, 2 and 3 years flying it.

I was told by one of my first 747 instructors on the 200 (An ex PanAm Clipper Skipper) 30 seconds after setting takeoff thrust you should be at 100 knots. Should not change more than a couple of seconds in an empty aircraft vs max TO weight. I have checked it with a stop watch MANY times. Works every time!

[Gabriel]

Put a little triangle or arrow pointing to the airspeed value in the speed tape that the airplane should have now. If the current airspeed is at or above that mark, go. If not, abort. It's that easy.

Using the actual airspeed instead of the acceleration will solve not only the slow acceleration but also the reduced headwind issue.

[3WE]

You don't think after flying the 74 for 15 years I can't tell when the aircraft is accelerating properly? Do you even realize the difference between ferrying an empty airplane vs one at max gross t.o. weight?

Other pilots, on this very forum, in the last two days have indicated that the variation in aircraft weight means that many pilots do not know if their plane is accelerating properly.

Yeah, when it's heavy, it accelerates slow...and when it's light it accelerates fast...I get that and have observed that with planes and cars and trucks....and I even took fiziks and they confirmed it.

What you don't get is that doesn't let me know if it's on target or not. And as Gabriel says, it's very possible that YOU have a good idea if you are on target. That doesn't means someone with 15 weeks flying a 747 one day heavy, one day light, one day inbetween, would 1) know if he's on target and 2) know if the winds have shifted.

On a really tight runway/takeoff situation, if a big headwind dies big time, you will reach one knot below V1 too far down the runway to stop- if you need to abort.

You'll probably live, but your nose tires might get some mud on them.

[Evan]

Put a little triangle or arrow pointing to the airspeed value in the speed tape that the airplane should have now. If the current airspeed is at or above that mark, go. If not, abort. It's that easy.

Using the actual airspeed instead of the acceleration will solve not only the slow acceleration but also the reduced headwind issue.

Better yet, just put a nice big caution light on the glareshield that says ACCELERATION or V1 ERROR or something with an ALARM when the system detects underspeed at the location where 80% V1 should occur. You get this alarm, you throw it in neutral and hit the brakes. Hey, it works for configuration.

Now how are you going to put a marker on the runway and make that work? You would have to have some type of system to move it back and forth for every aircraft on every takeoff for the conditions of the aircraft and the MET.

BB, I think the idea is that you put a marker at a fixed location on the runway. When the a/c passes that marker it must be travelling at a reference speed calculated by the FMC (some percentage of V1) to be performing as expected. So the marker is fixed but the calculated reference speed is what moves up and down based on takeoff criteria.

The new routine would be: 80kts, Vx, V1, Vr... (Vx for acceleration reference speed, unless Vx is already taken....) At Vx callout, the PNF visually looks for the marker and calls 'check' or 'positive acceleration' or something.

[BoeingBobby]

Better yet, just put a nice big caution light on the glareshield that says ACCELERATION or V1 ERROR or something with an ALARM when the system detects underspeed at the location where 80% V1 should occur. You get this alarm, you throw it in neutral and hit the brakes. Hey, it works for configuration.



BB, I think the idea is that you put a marker at a fixed location on the runway. When the a/c passes that marker it must be travelling at a reference speed calculated by the FMC (some percentage of V1) to be performing as expected. So the marker is fixed but the calculated reference speed is what moves up and down based on takeoff criteria.

The new routine would be: 80kts, Vx, V1, Vr... (Vx for acceleration reference speed, unless Vx is already taken....) At Vx callout, the PNF visually looks for the marker and calls 'check' or 'positive acceleration' or something.

V1 is the critical engine failure recognition speed or takeoff decision speed. It is the decision speed nominated by the pilot which satisfies all safety rules, and above which the takeoff will continue even if an engine fails. The speed will vary between aircraft types and also due to aircraft weight, runway length, wing flap setting, engine thrust used, runway surface contamination and other factors.

The US Federal Aviation Administration defines it as: 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.


A. Vx is best angle of climb.

B. Are you going to have markers for lets say, 737,747,757,767,777 etc?

Do you now see how ridiculous this would be? There would be 25 different markers down the runways.

Gabriel's thought is to once again add some more information into the PFD. Just another circuit on a chip to generate yet another V speed, triangle naked lady silhouette or what ever. There is already plenty of things to be looking at. V1 works, that is why it has been used for so many years. There are too many variables to deal with with different aircraft types, weights etc.

"At Vx callout, the PNF visually looks for the marker and calls 'check' or 'positive acceleration' "

What are you going to do when the visibility is down?

You guys read to much into these incidents/accidents. Shit happens! Put a human being behind the wheel of a machine that moves and there are going to be problems from time to time. It has to do with statistics. It just so happens that it sounds so sensational when an airliner screws up because of the amount of people that it carries. Have someone find out how many people died in a one week period in JUST General Motors cars world wide. Lots more than a wide-body drilling itself into the ocean or ground with 300 pax and crew on board.

"you throw it in neutral and hit the brakes".

This one really cracked me up! THROW IT IN NEUTRAL!! What do you think this is, a John Deere?

Soon there will be no one in the cockpit at all, and the fabulous computers and electronics will take care of everything. That is when I start going by boat!

[Evan]

B. Are you going to have markers for lets say, 737,747,757,767,777 etc?

No, read what I wrote there. The marker could be at the same location for any a/c at any weight in any conditions because the reference speed would be different for each a/c. It seems like it would be a decent second line of defense.

"At Vx callout, the PNF visually looks for the marker and calls 'check' or 'positive acceleration' "

What are you going to do when the visibility is down?

I subscribe to Gabriel's idea of the internal guidance-based system for the primary line of defense. I do agree with you though that we don't need more bugs on the PFD so I think a simple caution/alarm similar to the configuration warning would suffice.

"you throw it in neutral and hit the brakes".
This one really cracked me up! THROW IT IN NEUTRAL!! What do you think this is, a John Deere?

Oh right, you drive an automatic ; )

Seriously, in the age of computer generated derated/flex power settings that maximize available runway don't you think pilots should have some clear indication of actual takeoff performance? I always thought a decent (fully awake) pilot could do this by instinct but apparently not.

[Gabriel]

BB, since you are a very experienced pilot in general, and in particular on the 747, I'd like to hear your opinion on this take-off. Is it normal?