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acjbbj
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Getting the shortest takeoff run

Mon Sep 03, 2018 12:00 pm

How could one get a fully-laden (at MTOW) 773ER up in the air with zero ambient wind speed and using the absolute shortest runway length? What is that shortest possible distance?
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GalaxyFlyer
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Re: Getting the shortest takeoff run

Mon Sep 03, 2018 1:55 pm

There are no “short field” techniques here—it’s static start, release brakes and wait for Vr, rotate at 2-3 degrees per second and go flying. And Boeing, among others including me, might argue about the need for standing or static start.

GF
 
trijetsonly
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Re: Getting the shortest takeoff run

Mon Sep 03, 2018 2:00 pm

Happy Landings
 
Redbellyguppy
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Re: Getting the shortest takeoff run

Thu Sep 06, 2018 6:18 pm

Perform a bleeds off static takeoff. Modify the flaps setting. In the 738 on a short field I might see flaps 25 for takeoff whereas on a long runway it will be more like flaps 5. There are second segment climb consequences to take into consideration for large takeoff flaps settings.
 
acjbbj
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Re: Getting the shortest takeoff run

Fri Sep 07, 2018 2:23 am

But you can't just expect shortest takeoff with full flap, right?
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Starlionblue
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Re: Getting the shortest takeoff run

Fri Sep 07, 2018 2:47 am

acjbbj wrote:
But you can't just expect shortest takeoff with full flap, right?


Correct. You're more likely to get the shortest run with a high flaps setting, but not full. Full gives more lift but the increase in drag is proportionally greater compared to the higher flap settings.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Max Q
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Re: Getting the shortest takeoff run

Fri Sep 07, 2018 11:57 am

Disagree on the static start

Turn on, keep it rolling and set
thrust without delay, then you have
10-20 knots in hand already

Why stop and have to accelerate
all that mass from a dead start ?
The best contribution to safety is a competent Pilot.


GGg
 
GalaxyFlyer
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Re: Getting the shortest takeoff run

Fri Sep 07, 2018 3:00 pm

How much runway is used “keeping it rolling and set thrust”. Line up alone from the taxiway can eat up 200’-300’.

The C-5 testing by Lockheed showed a static start was worth 750’ of distance and that penalty was applied to rolling take-offs. Boeing, however, would tend to agree with you but not entirely. A lightweight take-off benefits from a standing start more than a heavy one. The heavy plane isn’t moving much while spook up is happening. A static take-off certainly feels more exciting.

GF
 
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trpmb6
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Re: Getting the shortest takeoff run

Fri Sep 07, 2018 5:07 pm

Max Q wrote:
Disagree on the static start

Turn on, keep it rolling and set
thrust without delay, then you have
10-20 knots in hand already

Why stop and have to accelerate
all that mass from a dead start ?


Engine spool up. I've often tried to figure out where the balance is. There's somewhere on a graph where the two curves cross showing which method is better. I think Galaxy above was alluding to this.

Edit: He ninja'd my post, read Galaxy's explanation immediately before this one.
 
Max Q
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Re: Getting the shortest takeoff run

Fri Sep 07, 2018 9:09 pm

[quote="GalaxyFlyer"]How much runway is used “keeping it rolling and set thrust”. Line up alone from the taxiway can eat up 200’-300’.

The C-5 testing by Lockheed showed a static start was worth 750’ of distance and that penalty was applied to rolling take-offs. Boeing, however, would tend to agree with you but not entirely. A lightweight take-off benefits from a standing start more than a heavy one. The heavy plane isn’t moving much while spook up is happening. A static take-off certainly feels more exciting.

GF[/quote
The best contribution to safety is a competent Pilot.


GGg
 
GalaxyFlyer
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Re: Getting the shortest takeoff run

Fri Sep 07, 2018 9:12 pm

And your post is........

GF
 
Max Q
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Re: Getting the shortest takeoff run

Fri Sep 07, 2018 9:24 pm

I’ve been able to turn on the runway, not leaving any behind with 10-12 knots, both engines spooled while lining up and thrust set when
straight, next to none runway left behind


I Still think it’s better than stopping
The best contribution to safety is a competent Pilot.


GGg
 
flyboy80
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Re: Getting the shortest takeoff run

Fri Sep 07, 2018 9:53 pm

Does a higher flap setting decrease the initial rate of climb despite getting the airplane airborne faster?
 
GalaxyFlyer
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Re: Getting the shortest takeoff run

Fri Sep 07, 2018 10:10 pm

How did you line up, have 10-12 knots and not compromise (start the roll) the line up distance used by performance engineering?

From Boeing Jet Performance Training Manual:

These lineup allowances are published in the Flight Planning and Performance Manual and another document called the “Takeoff Safety Training Aid”. The allowances are provided for a 90° turn onto the runway, and for a backtrack followed by a 180° turn. It should be noted that these are the minimum possible line-up allowances for these maneuvers. Actual line-up allow- ances will depend on flight crew technique but will not be less than these published minimum val- ues.

GF
 
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Starlionblue
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Re: Getting the shortest takeoff run

Sat Sep 08, 2018 12:10 am

flyboy80 wrote:
Does a higher flap setting decrease the initial rate of climb despite getting the airplane airborne faster?


Yes.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Max Q
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Re: Getting the shortest takeoff run

Sat Sep 08, 2018 3:39 am

GalaxyFlyer wrote:
How did you line up, have 10-12 knots and not compromise (start the roll) the line up distance used by performance engineering?

From Boeing Jet Performance Training Manual:

These lineup allowances are published in the Flight Planning and Performance Manual and another document called the “Takeoff Safety Training Aid”. The allowances are provided for a 90° turn onto the runway, and for a backtrack followed by a 180° turn. It should be noted that these are the minimum possible line-up allowances for these maneuvers. Actual line-up allow- ances will depend on flight crew technique but will not be less than these published minimum val- ues.

GF




No matter how carefuly you turn on you’ll leave some runway behind


Obviously when you enter the runway as close to the end as possible and make a ninety degree turn to line up you’ll minimize
this, you can certainly maintain 10 knots in that turn while getting equally spooled


Once lined up, it’s immediately autothrottles on and you’re off


Preserving momentum and using all
possible runway


The static technique only addresses the second part of that equation



Put another way


I’d rather be at the beginning of the runway with 10 knots in the bag already and full power set
The best contribution to safety is a competent Pilot.


GGg
 
cpd
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Re: Getting the shortest takeoff run

Sat Sep 08, 2018 4:02 am

acjbbj wrote:
How could one get a fully-laden (at MTOW) 773ER up in the air with zero ambient wind speed and using the absolute shortest runway length? What is that shortest possible distance?


Well, I've seen SIA get a 777-300/ER off the ground at Sydney (RWY34L) from around A4. ATC gave them a bit of hurry up, another plane was approaching - so they were asked to go "as quickly as you can please".

No idea what kind of load they had, but probably not full fuel load. They turned onto the runway and didn't pause.
 
MatthewDB
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Re: Getting the shortest takeoff run

Sat Sep 08, 2018 4:47 am

Years ago I was transiting in Phoenix when a sandstorm whipped up. They announced to board quickly and that all airplanes were promptly departing. I was in a 757-200. We pushed back before everyone was seated, and the pilot announced that we were cleared for #1 departure and we took off at the fastest taxi I've ever had. We zipped across the overpass at the east end and rolled onto the runway. The pilot was spooling up as we turned and we were gone.

I remember looking down before we were past the terminals and seeing the airport emptying out.
 
BA777FO
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Re: Getting the shortest takeoff run

Sat Sep 08, 2018 12:17 pm

Only other thing to consider with the 777 and a rolling takeoff run is that you need the main gear steering to center otherwise uou'll get a takeoff config warning if you set takeoff thrust before it's centered and locked.

And that slows everything down!
 
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AirKevin
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Re: Getting the shortest takeoff run

Sat Sep 08, 2018 2:17 pm

BA777FO wrote:
Only other thing to consider with the 777 and a rolling takeoff run is that you need the main gear steering to center otherwise uou'll get a takeoff config warning if you set takeoff thrust before it's centered and locked.

And that slows everything down!

I assume this is also the same with the 747.
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SaveFerris
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Re: Getting the shortest takeoff run

Sat Sep 08, 2018 4:02 pm

AirKevin wrote:
BA777FO wrote:
Only other thing to consider with the 777 and a rolling takeoff run is that you need the main gear steering to center otherwise uou'll get a takeoff config warning if you set takeoff thrust before it's centered and locked.

And that slows everything down!

I assume this is also the same with the 747.


You are absolutely correct, you will get a Takeoff Config warning when either engine 2 or 3 are set to to takeoff thrust and the body gear steering is unlocked.

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