Radio / radar altimeter applications on turbo props

[TheInsider]

So my understanding is, if you are not applying the instrument for a cat II or III you should simply leave it at zero and keep it in the scan for situational awareness. Anyone else have any other cool applications they use it for?

When I flew props with RADAR altimeters (no CAT II), for sit. awareness, I would set it to 2000' in mountainous terrain and 1000' in non-mountainous. On approach I would always set it to 50' above DH and 100' above MDA.

 

[yournextFO]

Also, some aircraft use the RA to adjust the autopilot gain when on approach (to prevent excessive A/P corrections as you get closer to the runway.)

The RA can also be used to inhibit the stick shaker and/or pusher near the ground. In fact, there are a surprising number of systems that tie into the RA, though probably more so on a jet than a TP.

 

[Bernoulli]

When I flew props with RADAR altimeters (no CAT II), for sit. awareness, I would set it to 2000' in mountainous terrain and 1000' in non-mountainous. On approach I would always set it to 50' above DH and 100' above MDA.

Good applications of the RA. I like it. Does anyone see any problems with the above applications of the RA if appropriate situational awareness is applied?

 

[Morettis]

Good applications of the RA. I like it. Does anyone see any problems with the above applications of the RA if appropriate situational awareness is applied?

I don't see a lot of point to setting it to 1000/2000 enroute because if you're IFR, as long as you fly the MEAs they guaranty terrain separation, and if you're VFR you should be looking outside and know exactly where the ground is.

Nothing wrong with setting it a little high for the approach to give yourself a warning that you're approaching your minimums and to start leveling off / looking outside.



The bottom line is that the Radar Altimeter isn't a primary instrument, its a supporting instrument. Just like the moving map on the GPS or an RMI, you don't get to do anything special because you have it, but if you use it correctly its one more tool to improve your situational awareness.

 

[trainer8]

So my understanding is, if you are not applying the instrument for a cat II or III you should simply leave it at zero and keep it in the scan for situational awareness. Anyone else have any other cool applications they use it for?

TCAS II uses the RA for operations below 1000' AGL while on approach. TCAS logic roles to TA mode only. Typically, if you MEL the RA, you also inop and MEL the TCAS by default.

And, as previously stated, EGPWS logic.

Many GPS's have their own terrain data base info, not requiring RA data.

T8

 

[PeanuckleCRJ]

The RA bug should always be off unless used for a cat ii/iii approach. Otherwise it is wonderful SA.

The only bug on a barometic only approach should be the MDA bug. The RA should never ever be used on a barometric approach.

 

[Tristar]

Not all RA bugs can be parked out of range, and it's a technique whether you use it or not in the ways previously suggested. There is nothing wrong with setting the bug as an additional alert (unless your companies procedures prohibit doing so).

However you are correct, you absolutely cannot use the RA on a baro approach to establish DH or MDA. I may not have made that adequately clear.

 

[av8tor19]

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.

 

[Sig]

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.

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.

 

[Mickey]

The Mooney Ovation I used to fly had one.