Line Up Allowance

[arrow28]

Hi everyone,

Can anyone please explain how the line allowance is applied to an intersection departure. Does it change depending on aircraft type and/or type of turn that is used to enter the runway? Is there a Jeppesen reference regarding line up allowance?

Thanks in advance

P28

[rudderrudderrat]

Hi arrow28,

Airbus produced a document "getting to grips with aircraft performance". It tabulates the distance used (for each aircraft type) in turning through 90 degs in order to line up. That distance must be considered for performance calculation.

"3.2.4. Loss of Runway Length due to Alignment
Airplanes typically enter the takeoff runway from an intersecting taxiway. The airplane must be turned so that it is pointed down the runway in the direction for takeoff. FAA regulations do not explicitly require airplane operators to take into account the runway distance used to align the airplane on the runway for takeoff. On the contrary, JAA regulations require such a distance to be considered:
JAR-OPS 1.490 Subpart G
IEM OPS 1.490
“JAR-OPS 1.490
(c)(6) […] an operator must take account of the loss, if any, of runway length due to alignment of the aeroplane prior to takeoff.” "

[mutt]

Does it change depending on aircraft type and/or type of turn that is used to enter the runway? Yep, aircraft and airline specific.

Is there a Jeppesen reference regarding line up allowance?
It really isnt their business unless they are producing the takeoff data for the airline.

For example we have some runways with arrestor cables built into them, for some aircraft with small tires we displace the threshold to beyond the cables so that the aircraft can taxi slowly over them. As this is aircraft specific its calculated as a line up distance rather than a displaced threshold.

Mutt

[arrow28]

Thanks Mutt and Rudderrat for your reply. I looked up JAR-OPS 1.490. However I am looking specifically for the line up allowance required for the Fokker 100/70.

Looked up CASA Australia and could not find anything there either. Will have to keep looking.


Thanks

arrow

[vineet.mk]

Hello Arrow,

Line-up allowance simply put is the "distance of runway lost to make the initial line-up and alignment to takeoff direction(by making turn etc)"

It is formalized in JARs but not in FAA. None the less, is recommended to be used by everyone.
Generally 180 or 90 or 0 deg line-ups are used.
180 where you need to back-track.
90 for intersections
0 where you have taxiways entering the runway from its undershoot area (don't know if they have a specific name for that)

I see there are 2 line-up allowances:-

Practical:- Which considers whatever runway lost by average crew to line-up (assuming they follow the taxiway markings)
You should look at line ops to identify this value.

Theoretical minimum:- This is the minimum your aircraft would to make that 180 or 90 deg turn.
This is directly related to the turning radius of the aircraft. Generally found in what is called as airport handling document.
JAA also requires publishing those values as min line-up.

Also 1 point, that line-up is different for reject case as compared to the go case.

Hope that helps.

VK

[arrow28]

Thanks for the input. I am looking in particular for the Line Up allowance for the F100.

Thanks

arrow.

[HazelNuts39]

arrow28;

Why don't you mail your question to: www.fly (http://www.fly)fokker.com/Services?