Does 'Runway Analysis' credit the runway not used prior to DER

[simonabadjian]

Dear All ,

My full question is:
Does 'Runway Analysis' credit the runway not used prior to DER with regard to obstacle clearance. i.e. If my airbus or gulfstream etc. can lift MAX structural in nice low density hight conditions in half the runway; will the APG software know that is the case, and account for the distance from the end of my TODR to DER, then add it to the distance from DER to OBSTACLE, when calculating the gradient to the obstacle and ultimately my MTOW for that runway.

If you have a reference too that would be helpful.

My understanding is that it does.

When I flew on AUST the old ERSA used to have a 'SUPPLEMENTARY TAKE-OFF DIST/GRAD' section. I understood that was the whole point of it!

Just need to settle a discussion amongst airmen. :hmm:

[john_tullamarine]

All depends on how the folk who set up the program went about their business. If the associated paperwork doesn't specify, then you should check.

However, you would be pretty safe presuming that the AFM distance data is used and then carried on to DER. It would make little sense to do otherwise - mainly due to the workload in splay obstacle assessment.

Caveat - the greater concern is tracking. Invariably (there may be the odd exception but I have never seen one), the OEI departure track will be based on tracking over DER so that you are placed in the normal departure splay. This will require positive ID at that point which often limited ceiling and visibility for departure pre GPS.

STODA data also is useful in the absence of Type A etc. - allows one to run up the STODA intersections as dummy obstacles which may provide some extra payload, especially if the Type has a first segment problem, as some do.

[Alpine Flyer]

The distance should be credited. Our IRTs have a list of obstacles considered and those are listed by distance from beginning of take-off run.

[john_tullamarine]

listed by distance from beginning of take-off run

Needlessly complex, I would have thought, for the typical jet runway with a number of intersections suitable for takeoff ?

[FlightDetent]

Depends on the SW used, really. I have seen it done both ways.

[Skyjob]

The operator has the option to define obstacles from takeoff end of runway or departure end of runway.
In either case, the runway distance is taken into account in the calculation.

[simonabadjian]

Thanks for the posts. Good old US aviation customer service payed off. See the answer from their engineer below.

Hello Simon,

When using APG data, you are correct that we take credit for the unused portion of the runway.

Your friend is conceptually correct regarding TERPS and PANS-OPS. Those criteria are built from the DER, but as you know we don’t recommend using those for obstacle clearance analysis.

In short, using our data will do exactly what you say in that we add the distance from the end of takeoff to the DER to the obstacle distances. We also adjust for runway slope to determine the height difference between the liftoff point and the DER.

[john_tullamarine]

and that would be typical of the approach taken by the great majority of ops engineers.