LDA/Glide Slope Approach: Precision?

[MasterFly]

I heard that at the ACA interview, they ask about an LDA/Glide slope approach, namely the LDA 6 in ROA. It is so hard to get a straight answer. The FAR/AIM says that an approach with an electronic glide slope (like this approach) is a precision approach, but many say since it is an LDA, it is still not precision. I can't make up my mind. This LDA does have a glide slope, but the course is about 10 deg. off the runway, so maybe it is not.

I was hoping Avbug could enlighten us on this!

Here is a previous post about this argument:

http://forums.flightinfo.com/showthread.php?s=&threadid=5583&highlight=lda

 

[hyper]

like groundhog day....

 

[walkthasky]

...

**CENSORED****CENSORED****CENSORED****CENSORED** that was some argument...
It still leaves the question in the air, because everyone's answer is justified. I personally think they ask the question to see your rational with it.

p.s. im going with precision..hehe

 

[pilotyip]

look it up

This whole topic was discussed about a month ago on this board, and fairly well defiend. I took the interview at ACA in 1996 and was asked the same question, I told the interviewer it was a non-precision approach because of runway line up, I was offered a job, he must have liked my answer.

 

[avbug]

14 CFR 1.1 clearly states that any standard instrument approach proceedure in which an electronic glideslop is provided, is a precision approach proceedure:

"Precision approach procedure means a standard instrument approach procedure in which an electronic glide slope is provided, such as ILS and PAR."

Alignment with the runway is not material to the question; precision is determined by the availability of both lateral and vertical guidance to a point in space (MAP at DA/DH). That particular point may be higher than standard, or farther from the runway than standard due to alignment issues, but that doesn't change the fact that precision guidance has been provided to that point.

An LDA proceedure without vertical guidance is a non-precision proceedure. An LDA proceedure with electronic vertical guidance (eg, glideslope) is a precision proceedure.

 

[walkthasky]

well said...

 

[flywithruss]

Not that simple ...

It takes more than Part 1 to answer this question ... to really research it requires an understanding of the rules governing instrument approach procedures when they're created. Yes, an approach must have electronic lateral AND vertical guidance to be precision. That's not enough, though. By that definition, an LDA-A (w/ GS) would be precision, even though it publishes NO straight-in minima. You just can't do a circling precision approach, by definition.

The rest of the definition requires alignment with the runway centerline, not to mention strict standards of course guidance, signal width, and the degree of accuracy of the signal involved. As a result, the ONLY precision approaches out there are ILS, MLS, and PAR ... GLS (precision GPS approaches) and TLS (transponder landing system) are likely to join the list in the near future.

To answer the original question, the LDA 6 at ROA is a non-precision approach, forever and ever, amen. The LDA/DME 19 and Rosslyn LDA 19 approaches at DCA (both of which have glide slopes associated) are also non-precision approaches. No LDA is ever precision, no matter what, because it does not provide the required alignment with the runway centerline. If it did, it would be an ILS! Some of us remember the old Kai Tak approach, the IGS 13, it was called (the "checkerboard" approach). Watch those airplanes (who had lateral and vertical electronic course guidance, per FAR 1) make that 47 degree turn to align with the runway at 300 feet and tell me how that is a precision approach!

I thoroughly understand the confusion here, but I've reached my conclusions only after discussing the matter in some detail with folks from two FSDOs as well as a good friend who is a DPE, and has also discussed it with the folks out in OKC.

These discussions are why I love this board ... I learn something new every day, and on a good day, I get to share it with the group.

Tailwinds, y'all ...

R

 

[The FNG]

I agree that an LDA approach with or without a GS is technically a non-precision approach. However, when there is a GS associated it is flown like a precision approach (with the exception of autopilot minimums). Both the FAF and MAP are determined using precision approach conventions rather than non-precision, and I believe this is what really matters.

 

[flydog]

In our Op Specs an LDA without vertical guidance is classified under Non-Precision. LDA with vertical guidance is classified as a "precision-like" approach whatever that means. In any case we are only authorized non-precision LDAs under 135 per our op specs

 

[MasterFly]

Thank you for your responses. I think this can be debated forever. According to FAR Part 1, it defines it as a precision approach, but it is still hard to call it one.

There is an LDA approach to DCA where there is a glide slope, but it takes you only to an MDA where you then have to fly around a building and fly visual down the river to the runway.

According to Part 1, it has a glide slope and is precision, but how can you really justify that this is a precision approach?