jedinein

So I'm out of KVNY heading to KLGB. I'm briefed and prepped for KLGB. KSNA is my alternate. I've got the charts pulled and am ready for KSNA, too. I'm even ready to return to KVNY, but that approach is over the rocks. It's IMC practically everywhere, the storm system we're in has IMC even at the usual out, the desert airports. I go partial panel, a vacuum failure, just south of POM (on the TEC route KVNY-KLGB for pistons). I'm approximately 5000' AGL over a bunch of airports. Should I dump my plan and dive for the nearby airports, struggling to keep control of the plane while pulling out the approach charts, briefing them, and hoping I miss the mountains that are on downwind, or should I proceed as planned and briefed, getting into KLGB or KSNA, whichever has the better chance of me landing successfully depending on weather and controller workload?

It's a great training scenario as closer is not always better. Partial panel, one may be better off sticking to the plan versus trying to pull a rabbit out of the hat.

For partial panel, a high scan rate is needed, but a high scan rate of the proper instruments. Assuming a vacuum failure that kills DG and AI, the TC and VSI are working:

If the TC is working, and one holds zero rate of turn, can the heading change?

If the VSI is working, and one holds zero rate of climb or descent, can the altitude change?

If one holds zero rate of turn, zero rate of climb or descent, and keeps the power the same, can the airspeed change? (Yes, but over a long period of time or in turbulence, we're talking about short term, next 30 seconds, kind of changes in somewhat smooth air. It's better to practice in smooth air and turn the turbulence on later.)

So if the heading, altitude, and airspeed can't change, why waste time constantly looking at those instruments? You can get faster information off of the TC and VSI. One also needs some good practice in making sure the plane is in trim, that will greatly reduce the IFR workload. It will also make an instrument failure easy to detect, the one that has failed is the one that is moving. (BTW, FRASCAs are great for learning to recognize instrument failures!)

Now the aircraft is under control, how does one navigate with a VOR? Turn in the direction the needle is moving until it stops. That is the reference heading. Roll out. Does the needle stay? If yes, turn 3 seconds at standard rate (approximately 10 degrees of heading change) towards the needle. That should get it drifting back towards center. If the needle starts moving, turn in the direction the needle is moving until it stops. When the needle is centered, take out the 3 seconds of heading change one did earlier. If that starts the needle drifting again, turn 3 seconds at half standard rate in the direction the needle is drifting.

The same technique works well for ILS localizers, except use half-standard rate turns or one wingtip low turns inside the outer marker if the needle is drifting. Once the course is set and the reference heading is found, one no longer needs to worry about a compass or what the heading is. Nor do we care about the winds.

The above is a quick and dirty summary of two books, four two-hour WINGS seminars, Lessons 1-14 in the instrument rating course that I teach, and several hours of proper practice in the FRASCA simulators. Once the students can trim, fly hands off, scan, and navigate, holding patterns become really easy. It's also in the holding patterns that many of the weaknesses of the previous pieces show.

Of course, when in actual IMC with a partial panel, someone had better be actively dying in order for me to accept a holding pattern, and then I'm demanding 10 mile legs, controller calling my turns, the no-gyro vectors, finding out where the alternates are and their weather, and so on. Even though I think I can handle it, there is no reason to not ask for the additional levels of monitoring and assistance. Pilots regularly die when partial panel.