c5load
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Does A 735 Really Need 2 Miles Of Runway For T/O?

Sat Jul 03, 2010 8:17 pm

I heard on KBWI Tower frequency that CO 1527, a 737-500 requested full length for rwy 28. Even if he is at MTOW, would he really need the full length of 10.520 ft? Why else would he tell tower that for planning purposes he would need full length?
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ajd1992
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RE: Does A 735 Really Need 2 Miles Of Runway For T/O?

Sat Jul 03, 2010 8:48 pm

It might be company policy, or it might be a temperature issue.

There's a whole host of things that are more than weight that can affect it.
 
dw747400
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RE: Does A 735 Really Need 2 Miles Of Runway For T

Sat Jul 03, 2010 9:03 pm

Over the past few days Winds have been light and variable at BWI. It's quite possible that the crew was expecting a tailwind on departure, and it would not surprise me if additional requirements are spelled out in he opspecs for tailwind takeoff.

I don't know exactly when this was, but flying at nearby Tipton airport just south of BWI where we've had to switch between 10 and 28 every few hours.

[Edited 2010-07-03 14:09:34]
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A342
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RE: Does A 735 Really Need 2 Miles Of Runway For T/O?

Sat Jul 03, 2010 9:33 pm

As always, the answer is: It depends.  

The official data can be found here (page 40 to 43):

http://www.boeing.com/commercial/airports/acaps/737sec3.pdf
Exceptions confirm the rule.
 
andyinpit
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RE: Does A 735 Really Need 2 Miles Of Runway For T/O?

Sat Jul 03, 2010 11:18 pm

C5,

I actually think I was working local for that flight, cause I even said to myself "he really needed full legnth?". If this is the same flight I'm thinking of this happened just a few days ago. The flight actually rotated just after the 28/33L intersection. The winds were out of the southeast and I'm sure they had more fuel on board because of the weather down in Texas, so that's what I'm guessing
 
wn700driver
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RE: Does A 735 Really Need 2 Miles Of Runway For T/O?

Sat Jul 03, 2010 11:19 pm

Could he have been going off de-rated? Lord knows we see a lot of Super 80s around here (KDFmightyW) doing the old B-52 take off, clearly at less than max thrust. And that's from runways that are right around 13401', elevation about 650msl. Just a theory anyway
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flymia
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RE: Does A 735 Really Need 2 Miles Of Runway For T/O?

Sat Jul 03, 2010 11:25 pm

It has been pretty hot in the BWI area the past few days no? If its a fully loaded flight with extra fuel for bad weather and high temperatures I am sure they will need a decent amount of runway, not the whole thing of course but rather have more then enough then not enough. Maybe just a SOP or just the Captains idea.
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Aesma
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RE: Does A 735 Really Need 2 Miles Of Runway For T/O?

Sun Jul 04, 2010 9:48 am

Rolling that long (had they really used most of the runway) wouldn't be a problem for the landing gear ?
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113312
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RE: Does A 735 Really Need 2 Miles Of Runway For T/O?

Sun Jul 04, 2010 10:17 am

The runway behind you is of no value for safety. The distance required to either accelerate to takeoff or accelerate, experience a malfunction and reject to a stop, is affected by a number of factors including altitude, temperature, wind component, weight and thrust setting used. With lots of runway ahead, a thrust setting can be used that provides takeoff performance similar to a maximum weight takeoff while still providing plenty of margin for a possible reject. However, making an intersection takeoff provides less margin in the case of a rejected takeoff and might also mandate the use of a higher thrust setting reducing the service life of the engines as well as greater environmental impact. Overall, it is more conservative to always use the full length available of any runway and that is the choice of many pilots and airlines.
 
kcrwflyer
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RE: Does A 735 Really Need 2 Miles Of Runway For T/O?

Sun Jul 04, 2010 3:10 pm

Quoting Aesma (Reply 7):
Rolling that long (had they really used most of the runway) wouldn't be a problem for the landing gear ?

They could roll all the way to Houston provided they dont exceed the maximum tire speed.


This reminds me of when the commutair B1900 would request full length of runway 5 at CRW for the short hop up to CLE.. and would then rotate in 2,000ft.
 
BigSaabowski
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RE: Does A 735 Really Need 2 Miles Of Runway For T/O?

Sun Jul 04, 2010 3:26 pm

Quoting andyinpit (Reply 4):
C5,

I actually think I was working local for that flight, cause I even said to myself "he really needed full legnth?". If this is the same flight I'm thinking of this happened just a few days ago. The flight actually rotated just after the 28/33L intersection. The winds were out of the southeast and I'm sure they had more fuel on board because of the weather down in Texas, so that's what I'm guessing

The CO crew probably does not fly to BWI all that often and did not know, while at the gate, that takeoffs on 28 are usually done from C. Thus they did not request the takeoff data for 28/C and it would've taken too much time/hassle to request the data and reset the speed bugs and thrust after they've started taxiing. The 735 is more than capable for taking off from C, however, all Part 121/135 flights require a runway analysis be performed before every takeoff.

[Edited 2010-07-04 08:27:12]
 
andyinpit
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RE: Does A 735 Really Need 2 Miles Of Runway For T/O?

Sun Jul 04, 2010 4:10 pm

Quoting BigSaabowski (Reply 10):
The CO crew probably does not fly to BWI all that often and did not know, while at the gate, that takeoffs on 28 are usually done from C. Thus they did not request the takeoff data for 28/C and it would've taken too much time/hassle to request the data and reset the speed bugs and thrust after they've started taxiing. The 735 is more than capable for taking off from C, however, all Part 121/135 flights require a runway analysis be performed before every takeoff.

First off...best user name I've seen yet.

And second that does make sense. It's not a big deal, there wasn't a need to get the flight out right away as we're usually 1 in/1 out anyway.
 
n6238p
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RE: Does A 735 Really Need 2 Miles Of Runway For T/O?

Sun Jul 04, 2010 7:17 pm

Isn't the 121 rule for takeoff limit the ground roll +30%? Add this with a tailwind, full load, and higher than standard density altitude I can't see how this would be too far from being possible to need everything to be legal.
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mandala499
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RE: Does A 735 Really Need 2 Miles Of Runway For T/O?

Mon Jul 05, 2010 10:07 am

Heaps of reasons...
Temp, derate, maybe other "problems" which are still go-items like no autospeedbrakes, or anti-skid inop, etc etc etc....

Coincidentally, I just had a look at the FPPM... on a 20K derate 737 classic...

Say flap 5, 30C, sea level... runway 28 is a positive runway gradient, but dunno how much, let's say 1% (it's probably less)... 10kt tailwind... you'd be limited to 58tons take off weight... now, if you're using the 18.5klbs engines, U'd be limited to a lower take off weight under those conditions... and yes, you'd need the full 10,500ft runway length to be legal...

Mandala499
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Goldenshield
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RE: Does A 735 Really Need 2 Miles Of Runway For T/O?

Mon Jul 05, 2010 10:23 am

Quoting N6238P (Reply 12):
Isn't the 121 rule for takeoff limit the ground roll +30%?

Mathimatically, it's done the other way around. Since a runway is a finite piece of land, the plane must takeoff using only 70% of the USEABLE runway surface at a given tempurature where a maximum takeoff weight is given. Then, things like slope, wind, derate, and MEL items, like an inop anti-skid are taken into account which will "move" that max weight until everything is accounted for and a final weight is prescribed.
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dispatchguy
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RE: Does A 735 Really Need 2 Miles Of Runway For T/O?

Tue Jul 06, 2010 1:39 am

Quoting Goldenshield (Reply 14):
Mathimatically, it's done the other way around. Since a runway is a finite piece of land, the plane must takeoff using only 70% of the USEABLE runway surface at a given tempurature where a maximum takeoff weight is given

Huh?

Where is that regulation? I thought it was that balanced/unbalanced field concept, at least for a Boeing bird (I know that at my carrier, our MD80 fleet is restricted to balanced field - since that aircraft wasnt certified for an unbalanced field, but our 57s and 67s all use the unbalanced field concept to maximize weight off a given runway). When we had 737s, they were done unbalanced field as well - to the max extent possible.

I know that AeroData likes to use unbalanced V1s to increase the weight one can lift off a given runway - but I dont think that CAL uses AeroData; and I would say that their Perf Engineering dept is pretty good.

Quoting mandala499 (Reply 13):
runway 28 is a positive runway gradient, but dunno how much

Simple rise over run - a 13 ft difference in runway end elevations over a 10502 length, multiplied by 100 is a 0.123 % slope.

I have the B735 SCAP file, but I dont know the obstacles off of 28 off the top of my head to be able to say what their max runway takeoff weight could have been...
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Goldenshield
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RE: Does A 735 Really Need 2 Miles Of Runway For T/O?

Tue Jul 06, 2010 2:08 am

Quoting dispatchguy (Reply 15):
Huh?

Where is that regulation? I thought it was that balanced/unbalanced field concept, at least for a Boeing bird (I know that at my carrier, our MD80 fleet is restricted to balanced field - since that aircraft wasnt certified for an unbalanced field, but our 57s and 67s all use the unbalanced field concept to maximize weight off a given runway). When we had 737s, they were done unbalanced field as well - to the max extent possible.

No, you're right. I was thinking landing. Dunno where my mind was.
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dispatchguy
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RE: Does A 735 Really Need 2 Miles Of Runway For T/O?

Tue Jul 06, 2010 9:28 am

Below is an output from the Boeing Perf Software, for a B737-500 (no winglets) with a 20K engine, Max V1 (not balanced field), Flaps 5, bleeds OFF - with a standard configuration, and an enforced minimum acceleration height of 1000ft AGL.

As you can see, whether they launched off of 28 full length, or 28-C, the max runway takeoff weight is the same, for the runway is obstacally limited off the departure end (assumng that the obstacles I have in here are correct).


Boeing Perf Software output for a B735 (no winglets) off of RWY28 Flaps 5


Now, if I do up a runway 28 Improved Climb, where these # are based on overspeeding the V-speeds to improved the 2nd segment climb, I get



For example, at 40C, my 2nd segment climb limit is 115200 lbs Flaps 5 bleeds OFF. Now, with a 0kt headwind, with standard V-speeds, my field length limit is 112900 lbs. BUT, if I overspeed the v-speeds, and use improved climb and trade a longer takeoff run for a better max weight in the 2nd segment of climb, I get a max runway weight of 121000 lbs.

Like someone else said earlier, its been a hot summer, and if they were carrying extra gas, they would want all the available field length possible - especially if they were basing their takeoff on an improved climb. At 40C their balanced field v-speeds are V1-134 VR-134 V2-141; now with improved climb their v-speeds are V1 and VR of 159 V2 of 163.
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wn700driver
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RE: Does A 735 Really Need 2 Miles Of Runway For T/O?

Fri Jul 09, 2010 3:18 am

Quoting Kcrwflyer (Reply 9):
They could roll all the way to Houston provided they dont exceed the maximum tire speed.

Um, as long as Houston's only 12 miles from there...

Aircraft Tires do not dissipate heat well, and will likely deflate (catastrophically) at anything much beyond that distance, at anything over taxi speed...
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