Our airline's runway analysis has a landing distance for landing beyond threshold and another one for landing beyond glide slope. For each distance it has the corresponding maximum weight allowable for that distance/runway.

My question is, what regulation or Ops Spec or other guidance addresses which landing distance you should use?

My assumption is that if you're on a visual approach, perhaps the beyond threshold distance is usable. If an ILS approach is used, perhaps the beyond glide slope distance is requied. However, we all know that one cannot descend below glide slope until necessary for landing. Is the beyond threshold distance ever permitted?

Any opinions or references to where this might be covered would be great.

Thanks!

 

I'd say it's best to always be conservative, and use the worst-case values. And really, even in visual landing conditions, most operators I've seen land on the slope, using it or not.

 

That's what I think as well. Just wondering what the legal "FAA" answer is. However, it probably is like most things and depends on the FSDO, POI, region, time of year, airport and who you ask.

Thanks for your reply.

 

Large airplanes are REQUIRED to use the visual glideslope (part 91) if conducting a visual approach. I would use the GS numbers unless you have specific guidance otherwise.

Maybe that's info for emergency situations?

 

Would your question be referencing legal requirements for Dispatch or airborne operations?

My carrier uses total landing distance available for the FAR requirements to dispatch (ie distance after glideslope not applied). Once in the air the AOM charts are used.

 

Airbum makes an important point, for turbojet dispatch 121 requires that landing weight allows a full stop within 60% of available runway (121.195 & 197).

Once airborne the only "requirement" is that you can get it stopped in the length of the pavement.

At all four of the 121 carriers where I've worked, runway analysis tables were used for dispatch and AFM landing distance tables were used for airborne reference. The runway analysis tables are typically generated by a third-party, but are based on manufacturer's data.

121 dispatch landing weight requirements are essentially based on a 50' threshold crossing height, ie: glideslope (121.195-197). Part 25 transport category airworthiness standards also dictate that landing distance data is based on landing from "a point 50 feet above the landing surface" (25.125). So, as far as I know, all of the manufacturer's data would essentially be based on landing "beyond glide slope" as your airline puts it. I'd be curious to know more about your tables, sounds like custom info that your company has requested or generated--though it would have to be based on manufacturer's data. Very interesting.

 

The FAR referenced, as stated, is applicable only to dispatch. To determine tha actual runway available for landing, Landing Distance Available (LDA), you need to look at the back of the 10-9 page. For the given runway there may be a number next the the published distance after glideslope. If this number is published then this is the legal LDA. If no number is in the column, then the LDA is the published runway length. Typically, Boeing will publish stopping distances that include touchdown 1000' down the runway. The glideslope may take you farther down the runway depending on GP angle. It seems your company has looked at both cases depending on approach type.

 

Just curious, what keeps you from just calling your company flight tech department or training department and ask them. When I come up with something I don't understand in the books, I usually just call them. That way you are assured to get the right answer, and not some guy on the line interpretation.

Just recently transitioned to a WB flying to destinations that had escape routes on the way. Had some serious questions about these, asked the guys I flew with and got many different answers. Finally called the flight tech dep that calculates the routes and got the real answers.

Same with these boards, great to get another perspective, but I would still start with your company.

 

I am new to this forum. How do I post a question about Landing Distance Beyond Threshold as it pertains to notes on the 10-9A page?

Thx
MSL007

 

Create a new thread in this forum if you like. Or you can just post it here since this thread topic is landing distance performance.