Following the GS

[minitour]

My company's ops specs require us to stay at or above the G/S during a visual approach.

What happens if the GS is NOTAMed out of service or you don't pick it up on the receiver? Just use the VASI/PAPI?

-mini

 

[mattpilot]

Just use the VASI/PAPI?

the Vasi & Papi are also GS indicators - it doesn't have to be electronic

 

[2000flyer]

From 91.129

(2) A large or turbine-powered airplane approaching to land on a
runway served by an instrument landing system (ILS), if the airplane is
ILS equipped, shall fly that airplane at an altitude at or above the
glide slope between the outer marker (or point of interception of glide
slope, if compliance with the applicable distance from cloud criteria
requires interception closer in) and the middle marker; and
(3) An airplane approaching to land on a runway served by a visual
approach slope indicator shall maintain an altitude at or above the
glide slope until a lower altitude is necessary for a safe landing.

 

[Dr Pokenhiemer]

Thanks 2000flyer---that's what I meant.

 

[minitour]

the Vasi & Papi are also GS indicators - it doesn't have to be electronic

Right...which is why I asked if thats what they use if the GS is out...

not for a basic thing but more of a "what does your company do" kinda thing...

Thanks for the insights guys!

-mini

 

[cessna_driver2]

What happens if the GS is NOTAMed out of service or you don't pick it up on the receiver? Just use the VASI/PAPI?

-mini

Shoot it as a localizer approach?

 

[minitour]

Shoot it as a localizer approach?

well....yeah of course if there are LOC only minimums on the approach plate....but we were referring to a visual

-mini

 

[Crosswind79]

I'll stay on it to DH....After DH, the glide slope is not accurate under a category one approach - only category II and III

 

[Dr Pokenhiemer]

Crosswind--got slap your instructor! Really hard!! If you look at the ILS approaches to 36R at CLT, you'll see that the ILS 36R as well as the CAT II and CAT III ILS's ALL have the SAME localizer freq. of 108.9. (I'm not going to say, "That being said" because I think it's stupid and overused.) Now, if the localizer is not accurate below DH, how can these airliners follow it all the way down with an RVR of 600 or less or do an auto-land? The pilots have to shoot 3 CAT III approaches in order to be quailified to do this on their own. (I think.) The localizer IS accurate, your average instrument rated pilot ISN'T accurate enough. It's like a VOR--the closer you get to the station the less correction it takes. Try it on your Microsoft FlightSim. you'll see what I'm talking about.

 

[avbug]

Aaah, microsoft sim. The definitive reality experience. Not.

The question has been raised as to weather the ILS is accurate below minimums (200' has been given, suggesting category 1). It's not an issue of weather or not the ILS is accurate, but weather it's flight checked.

A category 1 ILS is not flight checked below minimums, and use of the glide slope below minimums is not authorized for vertical guidance. You can certainly reference it, but you cannot rely on it.

If that ILS has Cat II or III minimums published for it, then it's flight checked right to those minimums. In that case, the glide slope will be approved and has been regularly proven to minimums, including touchdown for Cat III with autoland, but the restriction then becomes one of pilot and aircraft, rather than the approach system.

It may be that the pilot is not approved for category II or III approaches, even though those minimums are published for the runway. The pilot may not descend below the Cat I minimums in this case, using the electronic glideslope for guidance, even though other minimums are published and the glideslop has been flight checked lower.

Bear in mind that many ILS don't go to 200'...many are higher. In these cases, the glide slope has been flight checked to the published minimums, and you may not rely on it below those altitudes.

In other cases, such as the Reno ILS (19R, I believe...foggy brain this AM), the approach goes to 1100 HAT. That's the decision height. However, approved operators are individually permitted the Silver ILS, which permits a 200' DH. In this case, the approach has been flight checked to 200', and the higher restriction and minimums are published in general due to missed approach and obstacle criteria. The silver minimums are assigned after an operator is able to demonstrate the ability to meet the higher climb gradient criteria from the lower DH.

To make a long story short, the issue of weather the glideslope is useable or reliable or accurate below minimums is superfluous. Who cares? It should be reliable, but may not be...but it's not legal for use below minimums, except as a reference. Further, it's not flight checked below minimums; you have no gaurantee.

Personally, I stay with the glide slope to touchdown, unless a visual indicator intervenes. If I'm on glideslope below minimums, visually landing and I start to get a low indication on the visual indicators, I'll reduce the rate of descent slightly to remain above the visual indicators, touch down a hair farther, and everybody is happy. When staying with the glideslop, I recognize that below minimums, I'm visual, and that I'm relying on my visual perception of the approach, and not the glideslope. It's now a reference, only.