gulfstream650
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737s Not The Best Braking Action?

Wed May 15, 2013 8:03 pm

This is a question that I have been wanting to ask for a while and after a recent trip (which made me ask the question again (three times)) - is the 737 not a very good at braking on landing?

After touchdown you seem to get a lot of noise and not much else compared to other types.

Would it also be correct to say that the 737 might have perhaps a few more than its fair share of runway overruns every year too?

Interested to hear your thoughts..............
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vikkyvik
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RE: 737s Not The Best Braking Action?

Wed May 15, 2013 8:19 pm

Quoting gulfstream650 (Thread starter):

Interested to hear your thoughts..............

The 737 is possibly the most widespread airliner out there. Given that, and that it probably operates into many airports with shorter runways than, say, a 747, I'd say you'll see a greater number of overruns.

Other than that, if you don't need to brake hard for any reason, why do so?
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flymia
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RE: 737s Not The Best Braking Action?

Wed May 15, 2013 8:32 pm

Given that the 737 is used at some pretty small airports like Key West I don't think it has a braking problem compared to any other airliner. Would be interesting to hear from a 37 pilot.

Can you explain a little more what you mean? The noise you are talking about, are you referring to the reverse thrust?
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Boeing77W
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RE: 737s Not The Best Braking Action?

Wed May 15, 2013 9:58 pm

Are your experiences on one particular operator (namely Ryanair) or a number of them?
 
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Starlionblue
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RE: 737s Not The Best Braking Action?

Thu May 16, 2013 12:24 am

Just like any other airliner, the 737 has had to pass extensive certification testing, part of which has involved demonstrating that it can stop in the requisite distance for the airports where it operates.

What you have likely experienced are landings where high deceleration rates have not been needed.

After landing at the old airport in Male I can tell you from personal experience that the 737, like any other airliner, has the ability to make you hang from the seat belt while braking.
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PGNCS
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RE: 737s Not The Best Braking Action?

Thu May 16, 2013 3:20 am

Quoting Starlionblue (Reply 4):
After landing at the old airport in Male I can tell you from personal experience that the 737, like any other airliner, has the ability to make you hang from the seat belt while braking.

Agreed Starlionblue.

Here's my take as a former 737 pilot. The brakes are fine, and are in fact one of the best parts of the aircraft. I have never had any concerns about landing distance or braking on that aircraft (I have not flown the heavier NG's with higher Vref speeds, however.) People who have read my comments here know that I attempt to be factual, but that I am NOT a supporter or defender of the 737, and, in fact, detest it. Since I'm defending the 737 brakes, chances are they are pretty good; vikkyvik was exactly correct when he said


Quoting vikkyvik (Reply 1):
Other than that, if you don't need to brake hard for any reason, why do so?
 
roseflyer
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RE: 737s Not The Best Braking Action?

Thu May 16, 2013 4:57 am

The 737 has 4 autobrake settings, so you may have been on a lower setting because airlines want to save brakes.

The 737-800 with the short field performance package can takeoff and land on a shorter runway than the a320.

Quoting gulfstream650 (Thread starter):
Would it also be correct to say that the 737 might have perhaps a few more than its fair share of runway overruns every year too?

The 737 does not have statistically more overruns. It probably has more overruns because there are over 5000 in current service. Landing distance is calculated, so overruns do not happen unless there are mistakes made in the landing, some operators like GOL use 737s on very short runways.
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L-188
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RE: 737s Not The Best Braking Action?

Thu May 16, 2013 5:31 am

The original nacelles on the first 737's had to be redesigned to the common shape we see on the -100 and 200 aircraft. the tailpipe had to be extended past the wing.

Whe the reversers kicked in they actually where lifting the wing making the the aircraft lighter on the mains and therefore making the brakes less effective.
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Dogbreath
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RE: 737s Not The Best Braking Action?

Fri May 17, 2013 7:46 am

As a B737-800 Captain, I can say that the braking action of this aircraft is highly effective. I'm not sure what your question is attempting to ask, but am assuming that you're saying that the use of engine reverse thrust noise produces a lot of noise without any appreciable braking action.

I can't comment on other types of aircraft other than Boeing and Lockheed, but the braking philosophy on the Boeing is such that the Autobrake setting will assure a deceleration rate according to the setting selected. For example, an Autobrake setting of 2 will deliver a deceleration rate of 5ft/sec. If engine reverse thrust is used after landing the deceleration effect is highest at a higher airspeed than at lower airspeeds. Believe me it is effective, but at only the higher airspeeds. The deceleration force from reverse thrust, at say a touchdown speed of 140kts, will be greater than 5ft/sec, and the wheel brakes will not be engaged till such a point that the effect from the engine reverse thrust reduces to 5ft/sec. At that point the wheel brakes will be automatically engaged to achieve 5ft/sec rate. There are many factors that will affect when this occurs, but this may occur at around 90kts airspeed. I personally reduce the engine reverse thrust at around 80-70kts (depending of course on runway length remaining, runways surface conditions, etc, etc). It may be that on your flights, the pilots have left the reverse thrust in till a much lower airspeed that's required for whatever reason. Yes, it does make a lot of noise at this crossover point and below, and in my experience doesn't provide much assistance in deceleration.

As has been mentioned before there are 4 autobrake settings for landing.
Setting 1 - 4ft/sec
Setting 2 - 5ft/sec
Setting 3 - 7.2ft/sec
Setting Max - 14ft/sec above 80kts, then reducing to 12ft/sec till stop.

Of course at ay time during the landing ground roll the pilot can override the autobrakes and manually brake as he/she requires. The autobrakes will be disarmed at this point. The wheel brakes are extremely effective on this aircraft.

Your comment about runway overruns, has absolutely nothing at all to do with the aircraft type. Human factors is the major cause of almost all overruns. There is an abundance of reports on the internet from EASA, FAA, CASA, etc that discuss the reasons for the number of overruns. On all these reports, no aircraft type is highlighted as a suspect. However the problems continue to be poor decision making skills from the crews concerned coupled with poor training, SOP, and lack of performance calculation/s.

If you calculate the runway length required (using reported and actual runway surface conditions for your landing), fly a stabilised approach (ie. on speed and on path), touchdown in the touchdown zone, a safe landing within the runway length is going to be the outcome (not withstanding major technical failure or a freak weather event). However time and again, there are skygods and cowboys that will continue with an unstable approach (high on path and high on approach speed), land half way down the runway, and then wonder why they run off the end into the mud.
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XT6Wagon
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RE: 737s Not The Best Braking Action?

Fri May 17, 2013 7:53 am

trust me, they brake just fine. The old WN 732's with the more er.... agressive pilots would often brake very hard to avoid back taxi.

NG are just as good when they need to be, but most airlines want more modest braking to keep tire and brake wear down.
 
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bikerthai
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RE: 737s Not The Best Braking Action?

Fri May 17, 2013 1:27 pm

Quoting gulfstream650 (Thread starter):

After touchdown you seem to get a lot of noise and not much else compared to other types.

Can you clarify the other types you are comparing? As other provided excellent comments on the braking systems, there may be other design differences among models that can explain the noise difference.

We are also assuming you are talking about the NG and newer models, as the first gen 737 are more or less different beasts in term of engines and thrust reversers.

bt
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L-188
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RE: 737s Not The Best Braking Action?

Sun May 19, 2013 12:52 am

It should be noted that one can be brought down in 3900 feet..........that is the Runway length at Dutch Harbor Alaska.
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BoeingGuy
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RE: 737s Not The Best Braking Action?

Sun May 19, 2013 1:48 am

Quoting L-188 (Reply 11):
It should be noted that one can be brought down in 3900 feet..........that is the Runway length at Dutch Harbor Alaska.

Yeah, AS flew the 737-200s in there but apparently the 737-400s aren't authorized for DUT.
 
737tdi
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RE: 737s Not The Best Braking Action?

Tue May 21, 2013 5:51 am

I can tell you this, as a non commercial pilot but as a qualified engine run/taxi mech. on 727s, 737s, 747s, DC10s, DC9s, and F/A 18As., the F-18 had the best braking, when you hit the brakes it stopped on a dime and gave you whiplash. As far as the commercial guys in the bunch mentioned, they all brake basically the same during taxi. It is a matter of rotor/stator. They are disc. brakes, just with multiple rotors and stators. I will be honest, I have only taxied the 747 twice and decided I did not want to be qualified for taxi/run. I was uncomfortable the whole time (this was for ... in San Antonio). I told them NO. I did not get paid anymore so it just was not worth the hassle. Imagine the liability if you were to cause an accident?.. DC10 I could do and did do several times.. When I hired on at SWA/WN the guys laughed because I took the turns on the taxiway a bit wider then them. I simply said the gear does not follow directly behind you. Most of them have never taxied a large aircraft. Nothing wrong with that, just don't give me crap. HaHa.

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musapapaya
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RE: 737s Not The Best Braking Action?

Tue May 21, 2013 8:55 pm

Is the thread starter trying to compare A320 and B737 braking action? If so, this is highly invalid. On a runway, there is a higher chance of an A320 able to vacate the runway at an earlier taxiway than a B737, because the A320 tend to have a lower Vref on comparable weights. I have asked that question myself.
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bikerthai
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RE: 737s Not The Best Braking Action?

Wed May 22, 2013 1:16 pm

Quoting musapapaya (Reply 14):

He was commenting on the higher noise on the 737. That was why I asked for clarification.

The 737 may have higher noise on braking because . . .

The thrust reverses may be of different type?
The 737 is definitely lower to the ground than an A320 - thus you may get more ground noise.

or a host of other reasons for higher noise from braking.

bt
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United1689
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RE: 737s Not The Best Braking Action?

Thu May 23, 2013 12:26 pm

Quoting Roseflyer (Reply 6):
some operators like GOL use 737s on very short runways.

Yes Gol flies out of SDU with their 737-800SFPs and the runway is only 4,341ft long. I have flown into SDU on Gol's 737-800SFPs and the braking feels like landing on an aircraft carrier, you are literally thrown forward in your seat. Also, there are no A320s at SDU because they cannot land there, but the 738 can...
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