B737NG steel brakes welding

[Yon Garde]

Interested to know if anyone knows of any Boeing flight test data on the real probabilty of steel brakes welding after a RTO. As we all know, the QRH NNM mentions "consider not parking the brakes unless evac is likely" however the aircraft still needs to be stopped in some way whilst the situation is assessed and it strikes me that the brakes are just as likely to weld with the brakes held on manually as they are with the parking brake set with the added possibility that the brake pressure is unconciously released as the CAPT deals with a fairly stressful situation. I have seen this numerous times in the sim.

Does anyone know if Boeing may have come up with a weight/ temperature combination under MBRW where welding was considered less likely?

Thanks in advance.

(editted cos I carnt spel)

[ManaAdaSystem]

Our NG's got carbon brakes, and as far as i know, brake welding is highly unlikely with carbon brakes.

[Dehavillanddriver]

As far as I am aware carbon brakes are not an option on the 737.

Why I don't know, but I asked Boeing about that and that was what I was told - but that was a couple of years ago.

[Shaka Zulu]

The 737NG has got carbon brakes, and you can really tell once they are heated up, cos they grip a whole lot better when they are warm.
so why you don't know, i don't, but i'm sure we have carbon brakes on the NG.
Carbon brakes won't weld, they just catch fire when overworked.

[IFixPlanes]

I also think, that carbon brakes are not an option on 737.
The 737s i have worked on have no carbon brakes installed and the AMM has also no entrys about it.
I have experience on HHI, Privat Air(LH), HLF and some privat BBJs.

@ManaAdaSystem + Shaka Zulu
Can you tell me your companys?

Ingo

[Dehavillanddriver]

Interesting isn't it!

I am sure that the 737 does NOT have carbon brakes, even as an option.

[Right Way Up]

NGs most definitely have the option for carbon brakes, but it seems very few airlines opt for them. Carbon brakes can be very expensive if not treated correctly!

[IFixPlanes]

I think that, when there would be an option about carbon, every Airline would jump on it.
The brake have a weight of approximately 90kg. Every kg that can be saved would bring a big advantage.

Carbon brakes can be very expensive if not treated correctly!True, but most airlines have learned to handle carbon brakes on their Airbus Fleet. ;)

[Right Way Up]

True, but most airlines have learned to handle carbon brakes on their Airbus Fleet
I agree, I have flown both the NGs and Airbus, and with correct guidance from the airline carbon brakes can save money, especially if autobrakes are used with idle reverse.

[Yon Garde]

Thanks for the replys so far chaps. I too have been reliably informed that carbon brakes are an option (albeit an expensive one) to be retrofitted to the B737NG.

They would obviously provide savings in delta burn/ fuel flow due reduced weight, but does anyone that has operated with them know if they provide improved field length limited performance figures for takeoff and landing? I assume this would require further test flying (expensive) to validate, but would be the only financial reason strong enough to convince the operators to spend the money retro-fitting them.

[ManaAdaSystem]

Actually Vol 2 does not say, buy according to our local "IFixPlanes" we have carbon brakes Cat A on our -700s and Cat C on our -800s.
The categories are printed in the top right hand corner on all the P.I. pages.
Cat A brakes are capable of 44 millions of foot pounds energy pr brake, Cat C 56 millions.

[Centaurus]

I flew for an airline in the Central and South Pacific region operating 737-200's There were three specific case of brakes welding on following mis-use. First one was at Manila, max weight take off on very long runway. The 80 knot check on take off showed a 20 knot discrepancy (due to, as it turned out, water in the pitot systen after heavy overnight rain).

The captain elected to continue the take off (he was in denial?) and asked the F/O for another airspeed call when the F/O IAS read 100 knots. In other words he delayed making a decision.

The F/O then called 100 knots and as the captain ASI was still in error, the captain decided to abort. He applied full braking and reverse and pulled up with 4000 ft to spare. He then taxied to the terminal, parked the brakes, blew the fusible plugs and welded the brakes on. Not very good airmanship.

Case 2. The chief pilot conducting training at an island runway 7000 ft long. This involved successive full stop landings, and as the wind was calm, after take off a dumb-bell turn was carried out to land on the opposite end of the departure runway. The gear was retracted after take off in each case. OAT 30 C. After 30 minutes of training meaning around six full stop landings, the aircraft was taxied to the terminal to await passengers. The brakes were parked and shortly after the fusible plugs let go. I don't know if the brakes welded on.

Case 3. Max structural take off on 11,000ft runway - wind calm good weather. "A" system failure after landing gear selected up. Captain held for 20 minutes to sort out problem and had no choice but to return for non-normal A system failure landing which requires manual dropping of the landing gear and flap 15 landing. Under these conditions the thrust reversers are operated by the standby hydraulkic system and are slow to operate due small capacity pump.

Captain lands nicely near max take off structural weight and goes for full reverse. As advertised in the FCTM somewhere, the thrust reversers are very slow to open and as it is years since the captain has done this exercise in the simulator, he thinks he has now got a double failure of the reverse thrust system because the aircraft is really speeding down the runway and bugger all decelleration. He stamps on the pedals and applies maximum braking by which time when the reverse does finally come good, he has already slowed down to a speed where reverse is now ineffective.
He stops the 737 on the runway with 4000 ft remaining, in the belief that with an loss of system A he has no nose-wheel steering. He then instinctively sets the park brake on while he talks to ATC. Soon after the fusible plugs do their job and the brakes then weld on. As the runway was 11,000 ft long, and being wise after the event, it could be argued that he stuffed up by not being aware of slow reverse operation with loss of system A and could have gone real easy on the brakes allowing the aircraft to use the full length.

Under high speed stop conditions where the brakes become very hot, one option is not to apply the park brakes which really clamps the brakes on 3000 psi, but simply after stopping, lightly apply gentle pressure to one brake pedal sufficient to prevent the aircraft from moving under idle thrust until chocks are inserted.

This may save one set of brakes if nothing else. I have seen this method used where brakes were hot after landing on very short wet runways. It works a treat as you can easily stop the aircraft from moving by holding just a teensy weensy amount of pedal on the wheel of your choice!