lehpron
Posts: 6846
Joined: Tue Jul 10, 2001 3:42 am

Can Airports Set A Thrust Limit?

Tue Dec 03, 2002 12:11 pm

I swear I read it off of Airbus' website as reason for the low thrust to weight ratio on A380, but I already looked there and can't find it. Maybe it was on Boeing's page with regards to 773ER...?

Anyways, is there such a thing as 'limiting the max thrust' @ T/O, does it have to do with those deflectors at the end of the runway? Or the noise level?

If I do find that link I'll be sure to post it in here for those of you who are interested.
The meaning of life is curiosity; we were put on this planet to explore opportunities.
 
XFSUgimpLB41X
Posts: 3960
Joined: Fri Aug 25, 2000 1:18 am

RE: Can Airports Set A Thrust Limit?

Tue Dec 03, 2002 3:42 pm

There are some thrust limitations with regards to noise- such as reverse thrust not being allowed. There is a thing called FLEX thrust where you take an assumed temperature and it derates the thrust setting- this is used at airports where there are noise restrictions. In addition you have what is called "close-in community" departures where the aircraft climb at V2+10 higher than the standard 1000 AGL accleration altitude. The airline pilots on here can give you more detail as I have limited exposure to the flex thrust concept.
Chicks dig winglets.
 
tulsarefueler
Posts: 41
Joined: Thu Aug 22, 2002 10:17 am

RE: Can Airports Set A Thrust Limit?

Tue Dec 03, 2002 7:58 pm

Not completely sure but i think you are mixing up 2 things at once. On the
engine deal, there is a thing called FADEC which limits the engines. That is
Full Authority Digital Engine Control which is on many of the newer airliners.
The easiest way to describe this is you overbuild the engine power wise and
then derate it down to a more reasonable thruat and that in the long run will
give you the same power but a lower fuel consumption. Best aircraft is the
Boeing 777. Some of the engines on it are capable of up to 115,000 lbs/thrust
each. The pilot may only have access to lets say 90,000 lbs/thrust per engine.
By overbuilding the engine and limiting it, it saves fuel and wear on the engine
since the engine doesn't have to be at full power. Lets say you now have an
engine max rated at 90,000 lbs/thrust each. On takeoff the pilot would have
to have the engines at full power, and since this is the absolute max that the
engine can do, it is causing a little extra wear and drinking a whole lot of more
fuel.

Now for the deflectors at the end of the runway it depends on the airport.
There are probably many reasons why they are there but mostly since there
might be a building or a highway on the other side of the blast fence.

On the noise level, I am not completely sure but I do know that certain aircraft
cannot operate at some airports due to the noise abatement procedures. That
mostly applies to the older aircraft for instance the 727,737-200,707. Since
the older engines are a lot louder at takeoff power that the newer engines.
That is where the FAA mandated the hush kit mods to all aircraft and they
have to be at a certain decibel level or below. My home in Tennessee, the
local airport banned some of older aircraft due to excessive noise. The mainly
banned the older Lears and Gulfstream's. To prove the noise difference, we
have several old Lear 24's that fly alot. At full power it sounds almost identical
to an F-16 at full power plus 1/4th afterburner. Thats loud. It all depends on the airport.
 
Rick767
Posts: 2613
Joined: Sun Jan 30, 2000 8:11 pm

RE: Can Airports Set A Thrust Limit?

Tue Dec 03, 2002 8:16 pm

"FLEX thrust where you take an assumed temperature and it derates the thrust setting- this is used at airports where there are noise restrictions"

Actually FLEX thrust settings (a la Airbus) are used whenever possible at all airports with sufficient runway length and appropriate conditions to preserve engine life by using less than full takeoff thrust (TOGA).

It works on an assumed temperature derate principle.

Airports themselves cannot limit the amount of thrust an aircraft can use, but can enforce noise restrictions which, if exceeded, normally result in a fine. Sometimes this also prohibits certain aircraft using the airport at certain times of day.

You must bear in mind that FLEX thrust settings or assumed temperature takeoff thrust derates are not permitted under many conditions, one of which is a wet or contaminated runway which happens quite often in the UK at this time of year.
I used to love the smell of Jet-A in the morning...
 
GE
Posts: 312
Joined: Sun Mar 26, 2000 5:01 pm

RE: Can Airports Set A Thrust Limit?

Wed Dec 04, 2002 2:30 am

Just to add on Rick767's post: FLX takeoff also cannot be performed when

- Braking action is reported less than good.
- Probability of windshear exists.
- Headwind adjustment has been used to increase the allowable takeoff weight.
- Takeoff is made with a tailwind.

There may be a few more but this is all I can recall.

Regards,
Russell J.
 
lehpron
Posts: 6846
Joined: Tue Jul 10, 2001 3:42 am

RE: Can Airports Set A Thrust Limit?

Wed Dec 04, 2002 9:49 am

Can limiting thrust also be due to vibration on the ground or other aircraft due to engines?

And what about Concorde, are there any such thrust restrictions on her?
The meaning of life is curiosity; we were put on this planet to explore opportunities.
 
Flightlevel
Posts: 68
Joined: Fri Jul 11, 2003 6:54 am

RE: Can Airports Set A Thrust Limit?

Fri Dec 13, 2002 12:52 pm

Do gusty winds warrant TOGA or full power takeoffs?
 
A320-addict
Posts: 249
Joined: Fri Apr 20, 2001 1:24 am

RE: Can Airports Set A Thrust Limit?

Sun Dec 15, 2002 2:31 am

He Rick767,


'You must bear in mind that FLEX thrust settings or assumed temperature takeoff thrust derates are not permitted under many conditions, one of which is a wet or contaminated runway which happens quite often in the UK at this time of year.'

Is it company policy for you to perform a full take off with a wet runway??!
At our company flex-thrust ( assumed temp) is perfectly possible with a wet runway.


thx  Big thumbs up




AA


 
Flightlevel
Posts: 68
Joined: Fri Jul 11, 2003 6:54 am

RE: Can Airports Set A Thrust Limit?

Sun Dec 15, 2002 7:58 am

AA,

While I'm not Rick, it is many airlines SOPs that full power must be used on a contaminated runway. It is possible to use FLEX, but it wouldn't be that safe.
 
GE
Posts: 312
Joined: Sun Mar 26, 2000 5:01 pm

RE: Can Airports Set A Thrust Limit?

Sun Dec 15, 2002 1:14 pm

FLEX takeoff is not used on the A320 when takeoff runway is other than dry.

Flightlevel: I think you are right. In gusty conditions, using full TOGA thrust will probably be better than using FLEX.

Regards,
Russell J.
 
Flightlevel
Posts: 68
Joined: Fri Jul 11, 2003 6:54 am

RE: Can Airports Set A Thrust Limit?

Sun Dec 15, 2002 11:31 pm

Thanks GE. I was thinking it would be safer, but if you are light and the wind gusts are light, I don't think you'd want to do a TOGA takeoff, you'd be up in the air real fast.
 
filejw
Posts: 312
Joined: Mon Sep 18, 2000 2:58 am

RE: Can Airports Set A Thrust Limit?

Mon Dec 16, 2002 5:33 am

GE. Other than dry?Depends on where you work . Flightlevel.Conditions dictate, 10g15 no,25g35 yes,windshear yes.
 
Flightlevel
Posts: 68
Joined: Fri Jul 11, 2003 6:54 am

RE: Can Airports Set A Thrust Limit?

Mon Dec 16, 2002 6:25 am

Thanks for clarifying that even mroe Filejw.  Smile
 
Rick767
Posts: 2613
Joined: Sun Jan 30, 2000 8:11 pm

RE: Can Airports Set A Thrust Limit?

Mon Dec 16, 2002 6:35 am

A320-Addict

"Is it company policy for you to perform a full take off with a wet runway??!
At our company flex-thrust ( assumed temp) is perfectly possible with a wet runway."


Yes we must perform a full thrust takeoff if the runway is contaminated. I'm never too concerned about doing this as braking action will always be slighly questionable in these circumstances. I don't know whether this is company or regulatory policy, but it's our SOP nonetheless.

We also can't do reduced-thrust takeoffs on intersection departures (regardless of the distance available from the intersection) or when Low Vis procedures are in force.
I used to love the smell of Jet-A in the morning...
 
Whiskeyflyer
Posts: 223
Joined: Mon May 13, 2002 3:07 pm

RE: Can Airports Set A Thrust Limit?

Mon Dec 16, 2002 10:59 pm

Regarding max thrust and engine lives, on the RR Spey is you average using 97% max thrust (using N2 figures) you can get up to 6000 cycles extra life on certain discs. This adds up to a big cost saving. Notice that its average thrust, so you are allowed to use the max (which is advised from time to time, so as to see if the engine can still generate it)
 
dnl65
Posts: 78
Joined: Fri Jun 22, 2001 5:52 am

RE: Can Airports Set A Thrust Limit?

Tue Dec 17, 2002 12:04 am

The simple answer is that airports cannot set maximum thrust limits. At least they can't without going through the process established by FAR Part 161. To date none have (since 1990) . There may be a few examples out there but they are all grandfathered.

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