Sad Realization

[Inverted]

It isn't the FAA it's the stopping ability of the brakes. Assuming a transport category airplane, you could very easily exceed the thermal capacity of the brakes with a reject beyond V1 even at weights below MGTOW.
F=MA

Bingo. Part 25 certification of accelerate stop, and landing distances in general are max braking. That is what landing distance is predicated on, as well as accelerate stop distance. Not to mention statistics show that more accidents happen when aircraft go off the runway from high speed aborts.

 

[Boyington]

Can we rename this thread "Let's just argue about everything!!!"?

 

[derg]

There are very few things we abort for in the high speed environment at my airline, which is 80 knots to v1.

Engine failure, fire or we're convinced the airline isn't going to fly when we pull on the stick, which is self-solving anyway I guess. V1 and VR are generally fairly close in dry runway environments so if you're on the runway significantly above V1 and VR, chances are you've already cooked your goose and will be the next contestant at the "Big Brown Desk Show".

 

[Hacker15e]

@amorris311

Oh noez! The military guy who wants to go to the airlines said "mission"! Obviously that means I'm not suitable to operate in the 121 environment, right? A mission-focused pilot won't put safety first, right?

Take a look at what I wrote. The airlines do have a mission: to move people safely from point A to point B. That's a proper term to reference the entire purpose that airlines exist for. @amorris311's airline even calls it a "Mission Statement" on their website:

http://www.compassairline.com/html/aboutus.htm

Compass Mission Statement is:

The safe and consistent delivery of airline services that exceed our customers’ expectations, at a cost that will bring them back!

There isn't -- or shouldn't be -- an inherent poison pill over use of such terminology by a pilot.

An intelligent and thoughtful aviator knows that the main difference between flying for the military and an airline is where the risk management line is drawn. In the military, occasionally mission accomplishment is more important than safety (although as the saying goes, a sound tactical plan is inherently safe). In the airlines, keeping customers, equipment, and crew safe is more important than any aspect of getting the pax to their destination on time.

 

[Inverted]

Can we rename this thread "Let's just argue about everything!!!"?

I would actually prefer to talk about how AMF pilots are the best of the best.

 

[snOOp]

Can we rename this thread "Let's just argue about everything!!!"?

But at the same token @Derg needs to create an "OP Makes Thread that Goes to 15 Mind Numbing Pages". That would truly be a holy grail of trophies to earn on this forum [emoji39]

 

[derg]

But at the same token @Derg needs to create an "OP Makes Thread that Goes to 15 Mind Numbing Pages". That would truly be a holy grail of trophies to earn on this forum [emoji39]

Would that be "Derg" or the "Royal Derg" we're talking about here?

 

[Bonanzaman]

I don't think I've ever gone back and forth so much on whether I should post to a thread so much.

I'm just going to say, this thread is crazy, and the people who are seeming to be getting worked up are definitely making impressions.

Edit for English.

 

[Dugie8]

If you go back to my original post on the subject, this is exactly what I said the military does as part of the TOLD computation.

I apologize, I missed all that then. Now, this is going to sound snarky but I'm not being snarky. If that is what you are saying, you've answered your own question. If you move V1 up your runway gets longer and it isn't linear.

A 378000 pound DC8 would require about 8000 feet of runway on an ISA SL day at max thrust. Any increase of V1 lengthens that distant ASSUMING the brakes can do it.

What you are proposing would artificially lower you MGTOW unnecessarily since at a heavier weight and lower V1 you can stop in less runway.

From a nice to know perspective, not limiting, you would still find that any reject speed above V1 (calculated for for any given weight) would only give you minimal cushion, taking into account acceleration rates.

My current ride has awesome brakes, MGLW landing distances sub 4000 feet by a fare margin. A mere 20 knot increase in ref (no flap landing) increases that distance by 45%. This thing can almost do two MGTOW rejects without blowing the plugs.

My point being, you are thinking the FAA and mfgrs have just come me up with some arbitrary method and your experience with airframes not governed by the FAA or "capitalism" is somehow an apples to apples comparison.

Balanced field is the best compromise between ability and safety without crews having to employ any real special procedures to obtain maximum ability.

Bad happens, mash brakes, airplane stop.

 

[Hacker15e]

My point being, you are thinking the FAA and mfgrs have just come me up with some arbitrary method and your experience with airframes not governed by the FAA or "capitalism" is somehow an apples to apples comparison.

Balanced field is the best compromise between ability and safety without crews having to employ any real special procedures to obtain maximum ability.

No, I don't think it is arbitrary -- it is just different and in some cases more conservative, and I'm wondering why one instead of the other.

It is all nice to say that "it is the best compromise between ability and safety", and that sounds like a great reason, but this assumes something that is not known. It assumes there's some different level of safety and reliability (not even better or worse -- just different) with an ARL-computed V1, which nobody in this thread, or in any other areas I've read, has shown. I don't see how a statement about BFL being the "best compromise" can even be made without a direct comparison to ARL-derived data.

Your discussion about brake energy is an interesting postulation, and could very well be part of the rationale, but outside of some factual comparison data is simply that -- a postulation -- and not an actual, factual reason. Yes, I understand the physics of how energy and momentum change compared to the linear increase in speed.

Again, if the hypothetical runway extends 10 miles beyond the point of engine failure, why is a BFL-calculated V1 the "safest" option?

 

[Dugie8]

I don't have a good argument against a ten mile long runway, you could coast to a stop in that distance.

For super mid biz jets and below an 8000 foot runway is excessively long under most ops, even wet.

My rational is coming from the fact that mfgrs aren't doing it since there is nothing from the FAA that prohibits it. It, being what you are suggesting.

I'd be curious to what the KC10 folks do.

 

[jynxyjoe]

This thread is so full of win.

 

[Hacker15e]

My rational is coming from the fact that mfgrs aren't doing it since there is nothing from the FAA that prohibits it. It, being what you are suggesting.

FAA Part 25 (and 23 for the commuter category) says exactly how the airplanes will be certified, and thus drives what testing the manufacturers do, which thus drives what test-derived performance data makes it into the technical manual as procedure.

I'd be curious to what the KC10 folks do.

Great question, but my guess is that they use the BFL-generated data that McD supplied with the airplane, since it was all ready an established transport-category aircraft when it was purchased.

When I flew the C-12 for the Air Force, Beechcraft's BFL-based TOLD was used.

 

[Dugie8]

Part 25 only says the brakes have to do X Y and Z. Nothing there says the brakes only have to be able to stop the airplane at a balanced field V1 abort

25.735(f)(2)

Basically if bombardier thought and could prove it testing wise that "your" method was viable they would do it.

 

[Boris Badenov]

My current ride has awesome brakes, MGLW landing distances sub 4000 feet by a fare margin.

Woah, congrats, when did you get out of the bitchjet?

 

[jynxyjoe]

Part 25 only says the brakes have to do X Y and Z. Nothing there says the brakes only have to be able to stop the airplane at a balanced field V1 abort

25.735(f)(2)

Basically if bombardier thought and could prove it testing wise that "your" method was viable they would do it.

Jesus stop. My penis can only get so erect.

 

[Hacker15e]

Part 25 only says the brakes have to do X Y and Z. Nothing there says the brakes only have to be able to stop the airplane at a balanced field V1 abort

25.735(f)(2)

Basically if bombardier thought and could prove it testing wise that "your" method was viable they would do it.

Fair enough point, but it isn't my method. It is the method that Northrop and McDonnell Douglas engineers and test pilots thought was best.

 

[Dugie8]

Fair enough point, but it isn't my method. It is the method that Northrop and McDonnell Douglas engineers and test pilots thought was best.

Apologies, I put your in quotes because you were advocating it

I think there is enough difference between military specific design aircraft and your run of the mill part 25 jet that it isn't possible to carry one procedure over to the other.

I have spoilers and TRs in addition to brakes what did a T38 have?

 

[Dugie8]

Woah, congrats, when did you get out of the bitchjet?

3 weeks ago.

Thank you sir.

Added the CL30 to my ticket today.

 

[Hacker15e]

I have spoilers and TRs in addition to brakes what did a T38 have?

Absolutely nothing. Little dinky tires and not even antiskid brakes. So, it definitely has a lot more trouble stopping than probably many other jets with a 150-knot Vr (and although it is a smallish airplane, it weighs more than #12,5K).