B737's. Releasing the park brake with chocks in place
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B737's. Releasing the park brake with chocks in place
After landing and when the aircraft has taxied to the terminal, it has always been Boeing policy for the parking brake to be released once the wheel chocks are in place. This was common policy for many aircraft types and was a precaution against setting the parking brake against hot brakes.
The current FCTM makes this point under the heading of Taxi Speed and Braking:
"High taxi speed combined with heavy gross weight and a long taxi distance can result in side wall overheating. Avoid prolonged brake application to control taxi speed as this causes high brake temperatures and increased wear of brakes. If taxi speed is too high reduce speed with a steady brake application and then release the brakes to allow them to cool. Braking to approximately 10 knots and subsequent release of brakes results in less heatbuild-up in the tires and brakes than when the brakes are constantly applied". Notice the words, "release the brakes to allow them to cool".
The shut down procedure in the current B737 series FCTM, states: "After the wheel chocks are in place: Parking Brake - Release".
On all landings there will be some heat build up and long taxi routes exacerbate that heat build up. It is quite possible to arrive at the terminal with brakes so hot that you cannot put your hand on the them without risk of heat injury. Indeed, in a Boeing 737 Operators Symposium of many years ago, Boeing reported that if the hand cannot be held on the brakes then by defintion the brakes were hot and appropriate precautions should be taken.
Most 737's do not have brake temperature gauges in the cockpit. The pilot has no accurate way of assessing the temperature of the brakes after landing or arrival at the terminal. Of course if he suspects the brakes are hot he might instruct the first officer (rank has its priviliges!) to go down the stairs to put his had on the brakes and check their temperature. . Fat chance of that happening in todays democracy...
Recently, an Australian operator changed its shut down procedure from the Boeing recommendation of brakes release after wheel chocks in place, to a revised policy of leaving the parking brake on after chocks in place. Clearly this is a significant change from over 40 years of 737 Boeing recommended practice. The Boeing published FCOM is unchanged however.
The apparent reason given by the operator for this brakes on policy is to "standardise" with other types of aircraft in it's fleet.
Hot brakes in the vicinity of ground personnel and equipment are potentially dangerous. That fact is well publicised in flight safety material. A casual observer might wonder why the pressing need to change a long established Boeing procedure (brakes release when wheel chocks in place) for the seemingly illogical reason to "standardise" with other fleet types. It's got this scribe tossed...
The current FCTM makes this point under the heading of Taxi Speed and Braking:
"High taxi speed combined with heavy gross weight and a long taxi distance can result in side wall overheating. Avoid prolonged brake application to control taxi speed as this causes high brake temperatures and increased wear of brakes. If taxi speed is too high reduce speed with a steady brake application and then release the brakes to allow them to cool. Braking to approximately 10 knots and subsequent release of brakes results in less heatbuild-up in the tires and brakes than when the brakes are constantly applied". Notice the words, "release the brakes to allow them to cool".
The shut down procedure in the current B737 series FCTM, states: "After the wheel chocks are in place: Parking Brake - Release".
On all landings there will be some heat build up and long taxi routes exacerbate that heat build up. It is quite possible to arrive at the terminal with brakes so hot that you cannot put your hand on the them without risk of heat injury. Indeed, in a Boeing 737 Operators Symposium of many years ago, Boeing reported that if the hand cannot be held on the brakes then by defintion the brakes were hot and appropriate precautions should be taken.
Most 737's do not have brake temperature gauges in the cockpit. The pilot has no accurate way of assessing the temperature of the brakes after landing or arrival at the terminal. Of course if he suspects the brakes are hot he might instruct the first officer (rank has its priviliges!) to go down the stairs to put his had on the brakes and check their temperature. . Fat chance of that happening in todays democracy...
Recently, an Australian operator changed its shut down procedure from the Boeing recommendation of brakes release after wheel chocks in place, to a revised policy of leaving the parking brake on after chocks in place. Clearly this is a significant change from over 40 years of 737 Boeing recommended practice. The Boeing published FCOM is unchanged however.
The apparent reason given by the operator for this brakes on policy is to "standardise" with other types of aircraft in it's fleet.
Hot brakes in the vicinity of ground personnel and equipment are potentially dangerous. That fact is well publicised in flight safety material. A casual observer might wonder why the pressing need to change a long established Boeing procedure (brakes release when wheel chocks in place) for the seemingly illogical reason to "standardise" with other fleet types. It's got this scribe tossed...
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Parking Brake Release
Sounds very much like a "new broom" wanting to be noticed. Surely, decades of worldwide operations and the manufacturer would have determined the best practice. Standardization is fine, IF it results in an improvement on established practice. How long does it take a pilot to digest "normal" procedures for the aircraft type he/she is operating? Not as long as some managers seem to think.
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The current FCTM makes this point under the heading of Taxi Speed and Braking:
Notice the words, "release the brakes to allow them to cool".
TeeEmm,
A couple of things.
We just do what the FCOM says or the whole operation turns to chaos. When we disagree, contact the Fleet Manager and wait unless the new procedure is unsafe, then use your command perogative and modify it but contact the Fleet Manager and inform him/her what you intend to do.
Brakes always build up less heat when applied firmly to bring speed down to under 10Kts then released until the next application is required. Riding the brakes will put the brake pack heat through the roof.
The reference to sidewall heating is about tyres - a passion of mine. Always keep taxi speeds to 20Kts and under, even less for long taxi and/or rapid turn arounds. Overheated tyres will let you down, literally!! There is a bit of history, look at the incidents of exploding tyres costing airframes over the years.
A couple of things.
We just do what the FCOM says or the whole operation turns to chaos. When we disagree, contact the Fleet Manager and wait unless the new procedure is unsafe, then use your command perogative and modify it but contact the Fleet Manager and inform him/her what you intend to do.
Brakes always build up less heat when applied firmly to bring speed down to under 10Kts then released until the next application is required. Riding the brakes will put the brake pack heat through the roof.
The reference to sidewall heating is about tyres - a passion of mine. Always keep taxi speeds to 20Kts and under, even less for long taxi and/or rapid turn arounds. Overheated tyres will let you down, literally!! There is a bit of history, look at the incidents of exploding tyres costing airframes over the years.
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tee emm,
Where I work the brakes stay set on all types including 737 and 737ng unless the crew have a hi temp indicated (767 etc) or they know they've had a long taxi, tail wind, short landing etc.
Same at previous employer.
Where I work the brakes stay set on all types including 737 and 737ng unless the crew have a hi temp indicated (767 etc) or they know they've had a long taxi, tail wind, short landing etc.
Same at previous employer.
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Although not operating 737s, we have had problems with hydraulic fluid becoming acidic by pyrolysis. With brakes set, any heat will transfer to the now stagnant fluid and, with carbon brakes in particular due to the higher operating temperatures, cause phosphoric acid derivative to be produced in the fluid. Heat also accelerates the effect of oxidation and hydrolysis. Both of which produce acids. After having made crews aware that the parking brake should be released once chocked, the problems have decreased considerably.
