TCAS and one-engine out operation
 

Most of the aircraft I flew so far, required TCAS to be set to TA ONLY in case of single-engine operation. There seem to be A/C, however, on which the TCAS will automatically disable CLIMB RAs in case of an engine-out condition.

Would appreciate any inputs on which aircraft have such a feature, and what it depends on whether aircraft have it or not. I have a faint suspicion that earlier TCAS software versions simply did not have the feature and aircraft manufactureres never bothered to implement/certify it once it was available.

Thanks for any vectors.

I don't know of any aircraft that have an automatic inhibit of Climb in the event of an engine failure but if you think about it logically, if you are at lower levels and have a climb capability on one engine, why stay in TA only? Worse case scenario would be meeting another aircraft coming the other way also in TA only then no-one moves and a collision is assured.

That's not how it works. If you are operating OEI, the TCAS on the intruder will issue an RA, while you do not "cooperate" in the maneuver. If the intruder flies the RA and do nothing, no collision.

GF

Unlikely I know but what happens if he is also single engine in TA only?

Don't drive home, Fly3, coz your number's up! :eek:

That is even less probable than having two engines, destined to fail, incidentally mounted on your plane.

Or, not at all unlikely, the TA is the result of traffic only squawking mode "A"

Boeing QRH procedure for TCAS TA-

-Look for traffic using traffic display as a guide. Call out any conflicting traffic

- If traffic is sighted, maneuver if needed.

I had an disturbing experience in a SIM once.

On a typical, mandatory, and well rehearsed TCAS RA item, we had been climbing against a generated target. TA was issued, we acquired the intruder visually, called ATC and did not manoeuvre based on TA, waiting for the RA.

Which never came. SIM glitch. As we pushed the nose down, clearing the traffic with about 1/3 the desired TCAS miss distance, all three of us shuddered.

"If traffic is sighted, maneuver if needed" and in the old school way of avoiding a collision it means turning to the right in any aviation jurisdiction. Pretty sure that rule has not changed. If a threat is imminent don't climb or descend, follow rules of the air and turn. Of course if you are IMC all bets are off.

That's not how it works. If you are operating OEI, the TCAS on the intruder will issue an RA, while you do not "cooperate" in the maneuver. If the intruder flies the RA and do nothing, no collision.

To my understanding that will only be the case AFTER you have selected TA Only.

If I am correct I have always thought it an unnecessary delay in the Engine Failure QRH that TA Only is No. 9 in actions. Any time you have a wounded bird I want to tell all over a/c around me that I can not necessarily respond to an RA. Some QRH's have TA Only much earlier. Why the delay with an engine shutdown? It takes 1 second.

To play Devil's Advocate for a second, if you have power and/or speed in hand after the engine failure because for, example, you are at light weighs or lower levels, why not reselect TA/RA for the protection it provides?

Sound idea technically, especially against non-TCAS equipped intruders (only mode C/S).

In practical terms, it is too complicated to train in an airline environment. I foresee some liability issues too, unfortunately.

Fly3,

You're NOT getting any "extra protection", the intruder will follow an RA and the miss distance will be as designed. The intruder is doing all the maneuvering without requiring the OEI plane to do anything. :ugh:

GF

galaxy.
You are assuming that the other aircraft has TA/RA on. They might not.

Guys
It is worth reading the Eurocontrol ACAS Bulletins. There are 19 of them now and you will find them here http://www.eurocontrol.int/publications?title=&field_term_publication_type_tid=233&year[value][year]=
Very good information.

MM

Fly3,

Correct, do you have the odds of two OEI TCAS-equipped planes flying a collision course? Vanishingly small, I'd submit.

GF

Yea. Murphy's Law applies though.

So the scenario is...

- Two aircraft, each suffering one engine out, are on a collision course.

- ATC is completely asleep to the situation (after all, two aircraft emergencies in the sector at the same time is pretty mundane)

- The one that has RA to climb cannot. The one that has RA to descend has no RA capability.

Rather than cursing the TCAS designers for their lack of foresight I suggest you just accept that this really is not your day!

- two aircraft on a collison course
- one with engine out, tcas equipped and non-MEL
- other with XPDR with altitude reporting but no TCAS
- ATC not available for resolution
- see-and avoid not available
- too close to avoid through DESCEND RA
- crew trained not to stall after OEI RA (or recover) :}

Last words heard: "I knew I should have called in sick."