Safety Publications/Articles

When up is down

Lessons from actual vacuum failures

The AOPA Air Safety Foundation's recent research project on spatial disorientation started out so innocently. "Your next project will be a research study that involves flying the Air Safety Foundation's Archer and AOPA's Bonanza," my boss said. This is great, I thought. What could be better than getting paid to fly?

Then came the catch. "While flying with each volunteer pilot, you'll induce a vacuum failure in flight and observe the pilot's reaction and ability to control the aircraft." On second thought, this might be more of a challenge than I anticipated.

As a flight instructor, I had flown with "strangers' before, but never simulated an emergency with this degree of realism. A real, unannounced vacuum failure? How would the pilots react? The worst-case scenario I could imagine was a panicked pilot with a heart condition. On the other hand, pilots are trained for this type of emergency and should be able to handle it... right?

The idea for this project originated a few years ago. After the John F. Kennedy Jr. accident, FlightSafety International (FSI) performed a similar study, for ASF, in its Cessna 208 and 210 simulators. While there was no indication of vacuum failure in the Kennedy accident, it was of interest to see how pilots might cope with such an emergency. A grant from Sporty's Pilot Shop helped to defray the costs. The results were enough to make any instrument-rated pilot cringe - 66.7 percent of the pilots could not maintain control of the aircraft, and 50 percent of the flights ended in a crash.

Then, in 2001, the FAA's Civil Aerospace Medical Institute (CAMI) performed a vacuum-failure study in its Cessna 172 Skyhawk and Piper Malibu simulators. The Skyhawk pilots did noticeably better than the Malibu pilots. Overall, the Malibu pilots crashed 27 percent of the time. However, of the subset who flew with a vacuum-driven directional gyro installed in place of the electric horizontal situation indicator, 83 percent of the pilots lost control and "crashed." The Skyhawk flights saw only an 8-percent loss of control. But, those were simulators. With CAMI's blessing and oversight, it was time to do the study in a real airplane.

I placed an ad on ASF's Web site, asking for instrument-rated pilots to volunteer to come to Frederick and participate in a research project evaluating pilot performance flying instrument approaches with new avionics. This was the cover story and the first of several "lies" (I eventually lost count). Hundreds of pilots, from the East Coast to the West, volunteered. Of those, 60 pilots were selected based on factors such as flight experience, currency, and age, to gather a wide range of pilots.

Since I would be busy playing the role of ATC and safety pilot - and possibly saving us from spiraling into the ground - recording equipment was used to capture each Kodak moment. A small camera was mounted in the cockpit to record the instruments, the outside view, and the audio. A GPS flight data recorder was used to record the flight path and altitude deviations.

The tests were conducted in day VFR conditions, and a view-limiting device was used. A piece of polarized material was placed across the glare shield to prevent cheating, and the same material was placed in the "eyeholes" of the hood. This effectively blocked an outside view.

A protocol was developed that required each pilot to fly the same flight path. Each flight began with a practice ILS approach so the pilot could get used to the airplane and flying under the hood. Then, on the missed approach from the ILS the pilots expected to go fly GPS approaches at a nearby airport. As "ATC," I gave them vectors. What they didn't know is that on the missed approach I had disengaged the vacuum system. (The engine-driven pump was disengaged by an A&P mechanic before the flight, so I simply shut off the standby.) That's when the fun began. I was tasked with saving the day in the event that a graveyard spiral or other life-threatening maneuver was imminent.

The Archer pilots all maintained control of the aircraft, although some of the partial-panel approaches were questionable. The Bonanza pilots didn't fare so well; 25 percent lost control. The Archer pilots averaged 6.9 minutes to recognize the system failure, while the Bonanza pilots recognized it in 3.1 minutes. (Note: The Archer failure included the attitude indicator and DG, while the Bonanza failure included the AI and HSI. The HSI has a warning flag on it, which helped pilots to recognize the problem.)

Before each flight, pilots were advised that I would act as ATC. It was surprising that many of the pilots did not utilize that resource. Only 28 percent of the Archer pilots and none of the Bonanza pilots declared an emergency to "ATC." An instrument failure is an emergency, and ATC should be notified. This is a wonderful discussion topic for CFIs and their students. By declaring an emergency, the pilot will get all the needed assistance from ATC, and no-gyro vectors should be requested as well.

When training for partial-panel flying, CFIs usually cover up the "failed" instruments and tell the student to fly the airplane. While those instrument covers seem like a form of torture for the student, flight instructors should encourage students to carry them in their flight bag and keep them within easy reach while flying. During the research flights, 28 percent of the Archer pilots and 6 percent of the Bonanza pilots covered the failed instruments. Those pilots flew the aircraft well and did not lose control of it at any point.

This is a great lesson for students - it's distracting to have failed instruments in view, especially instruments that are part of the main scan. Cover them up and there's less work - less to look at! If you forgot your instrument covers, use pieces of paper or dollar bills. (Ones work as well as hundreds.) An instructor once told me that he never flies with less than two dollars in his pocket - you just never know.

These are some lessons that I learned, and hopefully you will share them with your students. After 41 flights, I witnessed egos being damaged, heard plenty of curse words, and had the privilege of flying with some excellent pilots. Most important, everyone involved walked away in one piece and with a greater respect for potential instrument failures and the skill required to cope with them.

Read the full report online (select number 02/19).

Kathleen Roy is a senior research analyst for the AOPA Air Safety Foundation. She is a flight instructor with multiengine and instrument ratings.

By Kathleen Roy

Back to the Index of Instructor Reports