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Does A 735 Really Need 2 Miles Of Runway For T/O?  
User currently offlinec5load From United States of America, joined Sep 2008, 917 posts, RR: 0
Posted (4 years 2 months 3 weeks 2 days 8 hours ago) and read 5159 times:

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?


"But this airplane has 4 engines, it's an entirely different kind of flying! Altogether"
18 replies: All unread, jump to last
 
User currently offlineajd1992 From , joined Dec 1969, posts, RR:
Reply 1, posted (4 years 2 months 3 weeks 2 days 8 hours ago) and read 5140 times:

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.


User currently offlinedw747400 From United States of America, joined Aug 2001, 1260 posts, RR: 1
Reply 2, posted (4 years 2 months 3 weeks 2 days 7 hours ago) and read 5123 times:

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]


CFI--Certfied Freakin Idiot
User currently offlineA342 From Germany, joined Jul 2005, 4682 posts, RR: 3
Reply 3, posted (4 years 2 months 3 weeks 2 days 7 hours ago) and read 5089 times:

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.
User currently offlineandyinpit From United States of America, joined Sep 2007, 320 posts, RR: 0
Reply 4, posted (4 years 2 months 3 weeks 2 days 5 hours ago) and read 5021 times:

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


User currently offlinewn700driver From , joined Dec 1969, posts, RR:
Reply 5, posted (4 years 2 months 3 weeks 2 days 5 hours ago) and read 5021 times:

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

User currently offlineflymia From United States of America, joined Jun 2001, 7176 posts, RR: 9
Reply 6, posted (4 years 2 months 3 weeks 2 days 5 hours ago) and read 5006 times:

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.


"It was just four of us on the flight deck, trying to do our job" (Captain Al Haynes)
User currently offlineAesma From France, joined Nov 2009, 6674 posts, RR: 11
Reply 7, posted (4 years 2 months 3 weeks 1 day 19 hours ago) and read 4797 times:

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


New Technology is the name we give to stuff that doesn't work yet. Douglas Adams
User currently offline113312 From United States of America, joined Apr 2005, 572 posts, RR: 1
Reply 8, posted (4 years 2 months 3 weeks 1 day 18 hours ago) and read 4781 times:

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.

User currently offlineKcrwflyer From United States of America, joined May 2004, 3817 posts, RR: 7
Reply 9, posted (4 years 2 months 3 weeks 1 day 13 hours ago) and read 4676 times:

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.


User currently offlineBigSaabowski From United States of America, joined Jul 2008, 158 posts, RR: 0
Reply 10, posted (4 years 2 months 3 weeks 1 day 13 hours ago) and read 4656 times:

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]

User currently offlineandyinpit From United States of America, joined Sep 2007, 320 posts, RR: 0
Reply 11, posted (4 years 2 months 3 weeks 1 day 12 hours ago) and read 4612 times:

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.


User currently offlineN6238P From United States of America, joined Jan 2006, 508 posts, RR: 0
Reply 12, posted (4 years 2 months 3 weeks 1 day 9 hours ago) and read 4492 times:

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.


To actively root against anybody is just low, and I hope karma comes back at you with a vengeance
User currently offlinemandala499 From Indonesia, joined Aug 2001, 6878 posts, RR: 75
Reply 13, posted (4 years 2 months 3 weeks 18 hours ago) and read 4216 times:

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



When losing situational awareness, pray Cumulus Granitus isn't nearby !
User currently offlineGoldenshield From United States of America, joined Jan 2001, 6041 posts, RR: 14
Reply 14, posted (4 years 2 months 3 weeks 18 hours ago) and read 4211 times:

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.



Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.
User currently offlinedispatchguy From United States of America, joined Jan 2006, 1249 posts, RR: 2
Reply 15, posted (4 years 2 months 3 weeks 3 hours ago) and read 3953 times:

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...



Nobody screws you better than an airline job!
User currently offlineGoldenshield From United States of America, joined Jan 2001, 6041 posts, RR: 14
Reply 16, posted (4 years 2 months 3 weeks 2 hours ago) and read 3934 times:

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.



Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.
User currently offlinedispatchguy From United States of America, joined Jan 2006, 1249 posts, RR: 2
Reply 17, posted (4 years 2 months 2 weeks 6 days 19 hours ago) and read 3837 times:

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.



Nobody screws you better than an airline job!
User currently offlinewn700driver From , joined Dec 1969, posts, RR:
Reply 18, posted (4 years 2 months 2 weeks 4 days 1 hour ago) and read 3427 times:

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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