Radio / radar altimeter applications on turbo props

[PeanuckleCRJ]

Note the CAT II into MSP on 30L.. that is a barometric only CAT II due to the terrain off the approach end.

Av8tor19, that is a good point about non-parkable (is that a word?) RAs... the previously described techniques would be appropriate- probably the 1000 foot being the most appropriate in most situations. However, even in the ratty King Airs I used to fly, the RA min bugs were able to be parked. So... this is just my logic when it can't be parked. Doesn't mean it's right (mainly becuase there really is no right answer as long as you aren't using it to base your approach off of it).

 

[Tristar]

Cat II airplanes also have to have 2 separate autopilots I think.

Actually, they don't (at least some don't). There are a lot of ways to get to Cat II - IIRC at ATA the 737 guys could hand fly a Cat II using the HUD. I know of several other aircraft which though they had two (or more) autopilots, could still operate Cat II with one deferred. Also, there was an article some years back in AOPA pilot on how you could qualify an average, well equipped single for Cat II. I don't recall the details, but it was possible (I belive it was related to an exemption for aircraft with a low approch speed - maybe Catagory A or something like that).

 

[trainer8]

DING DING!

I (thought) I posted this earlier, alas- I'm an ass.


Try using the RA on a CAT I ILS into BGM, AVP, CRW... it is cute to watch, but absolutely irrelevant.

It helps our NDs who have lost their depth perception to know when to flare the Dash. The ones who don't use RA use the old "saw" technique: Pulling back and forth on the yoke until the plane finally contacts the runway.

Good times.

Indeed. We could start a whole new thread on landing techniques of the Dash-8. I used to get so agitated at the "saw" landers. You'd thing they put different length main gear struts on various S/N numbered Dash-8s 'cause these guys would feel their way down.

T8

 

[Donsa320]

To answer your question, Cat I operations, the DH is a barometric reading and the RA is a backup. CAT II/III, the approach area around the runway (I don't know how far out) is surveyed and leveled. That is why you can use the RA for decision alt. The runway has to be certified as well as the plane. Cat II airplanes also have to have 2 separate autopilots I think.

All of our DC-9's and 15 of our 18 B-727's at the old Republic Airlines were CAT II with only one auto-pilot. I think you are confusing that with auto-land which is not required for CAT II.

Three of the 727's were leased and had flight directors which always went to GA when the auto-pilot was disconnected in approach mode. The Feds did not like that so ...no CAT II.

DC

 

[WMUSIGPI]

All of our DC-9's and 15 of our 18 B-727's at the old Republic Airlines were CAT II with only one auto-pilot. I think you are confusing that with auto-land which is not required for CAT II.

Three of the 727's were leased and had flight directors which always went to GA when the auto-pilot was disconnected in approach mode. The Feds did not like that so ...no CAT II.

DC

I wouldn't like that either......

 

[belchfire]

I don't know that they can't do Cat II and III, but many aren't equipped or trained. EGPWS still uses RADALT, so it's gotta be on the plane, anyway.

I think many planes display it, but don't really use it.

GPWS and EGPWS use radar altimeters to generate various terrain and configuration alerts required on multi engine turbine equipment.