When Your World Rolls Over

May 2, 2008 by Bruce Landsberg

If you ask a roomful of pilots how many have suffered a vacuum pump failure usually one third to one half raise their hands. When asked how many have had things go South in IMC the number is much smaller but still significant. Anyone who has ever had to fly partial panel in the clouds will not soon forget the experience.

If you’d like to hear how the story unfolded for a pilot down in Florida recently, watch this real pilot story. You’ll see first hand what worked well and what the pilot would have done differently. We are all “supposed” to be able to fly partial panel approaches under Part 91 ( personal) flight operations. However, I find it intriguing that the airlines and most corporate flight departments who operate with two person crews that fly more in a month than some of us do in a year, don’t put their eggs into that high-risk proficiency basket.

Their aircraft are all equipped with backup systems that pretty much eliminate all the heroics associated with a single point failure. Dry vacuum pumps are not especially reliable and even when the mandatory replacement schedules are adhered to religiously that is still no guarantee, as the real pilot story above shows.

Here’s the real solution if you fly much IMC or at night: invest in a backup power source and/or some alternate instrumentation. This does not relieve you of the responsibility to practice partial panel occasionally but it’s very comforting to know that if and when it happens to you, the belt and suspenders on a flight-critical system will be far superior than depending on the weakest link. If you like to learn more on the strengths and weaknesses of your vacuum system go to http://flash.aopa.org/asf/pneumatic_systems/.

Your thoughts:

A. Don’t do much IMC or night, so not an issue

B. I have a back up system

C. Backup is not needed – you’re supposed to be able to fly partial panel

Bruce Landsberg
Senior Safety Advisor, Air Safety Institute

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  • Hugh W. Larsen

    I have had more than one vacuum system failures in IFR conditions. Flying partial panel is practical. It is a lot easier with a Garmin 396. I had an electrical system failure a few weeks ago in unfamiliar territory and found the Garmin 396 to be extremely helpful. I have been flying a Cessna T210 for over 40 years. I think the Garmin 396 I have with XM weather is the best safety improvement so far. I do have another IFR certified GPS, but that quits when the power shuts down and it does not display weather.

  • Dan MacDonald

    Count me into the group having a pump failure (I have been flying long enough that I have had just about everything fail, and a few things twice). Although the incident I’m thinking of happened in actual IMC, I had just entered the clouds and made a 180 using the turn coordinator.

    My current plane has a King electric HSI, and an electric turn coordinator that drives an STEC 50 autopilot. My horizon is driven by a wet pump. I find myself flying approaches using the HSI more than the horizon anyway… so my risk has moved from the pump failing to an electrical failure! The plane has a relatively new alternator, and brand new extra capacity Concorde RG battery… and I often check the ammeter in flight.

    With current knowledge favoring the old wet pumps, I’m surprised the industry hasn’t moved that way.

  • Larry Martinez

    Living in Washington state I have flown a lot of IFR over the Rockies and at night. I fly a Turbo Arrow and had a standby vaccum system installed when I bought the airplane. I have had to use the standby system twice in IMC in the 22 years I have owned the Arrow. I would NOT want to fly partial panel in rough weather over the Rockies.

  • Jack Ellis

    Only a few hours after I received my instrument ticket, I had a brief encounter with ice in a rented Archer during which my pitot tube froze while over unfamiliar mountainous terrain and about to commence an instrument approach. The KNS80 became my airspeed indicator. It wasn’t comfortable and it wasn’t fun but it also turned out to be relatively uneventful.

    Some won’t like to hear this but in my particular case, partial panel proficiency, ability to use the electric turn coordinator, and heading and altitude information from a GNS 430W are enough redundancy. Flying in “hard IFR” out west entails dealing with larger hazards and risks than a vacuum loss. Backup GPS, backup power and backup instruments are just not cost effective for the hour or two at most that I might find myself in clouds or fog over the course of a year.

  • Jim McJoynt

    Hi Bruce – I have in my 7000 hours of flying had seceral failures of vaccum systems. Yes, I have back up electric instruments, and yes they were fine.
    The new issue is back ups in the G1000’s that are in all the new aircraft. I just had a full electrical failure in a New DA40 while ferrying to Fl from CA. I had less than 20 minutes to get to a suitable airport before the whole system shut down, including the backup Electrical Artifical Horizon. I had to use my personal hand held for communications and my personal GPS for Nav. I am getting a 496 for my flight bag, since that also has an artifical horizon, my BU GPS does not. There is not many ways to limit the draw on the G1000 it is a all or none system. There is NO needle Ball to keep you upright if you happen to be IMC or on top. The new systems are great, but some good old back ups are very necessary too.
    Regards – Jim McJoynt 00512377

  • Don J Miller

    Had vacuum and electrical failures at IMC with several different A/C and have found the 496 to be a great backup in addition to always knowing where VFR exists. Big changes since my first aircraft in 1968 but the basics always apply. Sorry that the new “electronic” pilots panic when you shut off the master switch, and that even freaks out most of the green instructors I’ve flown with. If you want to shake up a Cirrus or Columbia saleman, switch off the master at 3000′ and see what happens. N81SC N1189P N36545

  • Rich Oleszczuk

    Was very interested in the”real pilot story” that happened in Florida. The photos showed an S-Tec 30 autopilot in the panel that was not utilizedaccording to the author/pilot. I experienced an attitude indicator failure a while back during an ILS approach in IMC. I engaged the autopilot and used it tocomplete the approach. The S-Tec is rate-based and doesn’t know that a vacuum system exists.

  • joe grimes

    I have backup AI, twin wet vacuum pumps and twin generators (Cessna 310) and obsess over maintenance. I suppose I will take what I get and not lose any sleep over it.

  • James W. Johnson

    I have experienced vacuum and electrical failures on seperate occasions during 25 plus years of flying single engine airplanes. I have a standby vacuum system (precise flight) as well as an s-tec autopilot to help out during a vacuum pump failure. I also keep a garmin 496 plus a hand held navcom on board in case of an electrical failure. I would not feel comfortable flying IFR without having backup systems in place.

  • Karl L. Roesch

    Most of the vacuum pump failures, I hear, are with dry systems.

    Why are there not more wet vacuum pump installations ? The oil recovery unt would add little weight to the installation


  • Dave Wilson

    I have a back up vacuum system and a back up electrical system. Both systems have failed in IMC prior to investing in the back up systems. I attempt to “train” at least every three months utilizing an instructor performing partial panel. The vacuum failure after installing the back up system in IMC was a “non” event; confidence and the plan working is a wonderful experience.

  • Kurt White

    My first vacuum pump failure came while I was earning my instrument ticket. My instructor had covered my attitude and directional gyro so that I could practice partial panel approaches. When we removed the covers to make one more approach with full panel, it was discovered that the vacuum pump had failed. That was a great lesson for me to keep current on partial panel.

  • Don Vreuls

    Have Mid-Continent Electric Attitude Indicators with 1 hour battery backup (and slip indicators) replacing the turn coordinators in both my single and twin. The twin has two vacuum pumps, and two alternators. Both aircraft have low vacuum warning lights (to help mitigate confusion should the attitude indicator slowly decay). Also, I check vacuum pumps for wear at each 100 hour inspection and replace them between 400 and 500 hours. I have Garmin certified GPSs in the panels, and a portable 496 for use in each aircraft offering battery operated GPS derived track, turn rate, altitude rate and altitude.

  • Chic Wilson

    I agree with those pilots commenting that a portable GPS with panel page is a practical, affordable, reliable backup. My Garmin 296 is quick and accurate enough to keep the aircraft upright and on course. Even an NDB approach is a no-brainer if that is your best airport option.

  • Cary Alburn

    I’m curious how in the “real world” the Precise Flite vacuum backup that draws from the intake works at any higher altitude. I’ve heard stories that at the altitudes we fly in this part of the country (typically 10-11 thou on a cross country, 7-8 thou more locally) they don’t provide enough vacuum to keep the gyros turning. Yet if they do work, that would be a cost effective consideration for my legally IFR little bird, whereas many of the other backups are really too pricey to consider. Any comment from real world users?

  • Dick Lawrence

    I’ll try- this is a partial answer because I’m not anywhere near my plane to see the table I created with the standby system. I did install a Precise Flight system on my ’68 Arrow and then disconnected the vac pump to calibrate it. My mechanic suggested that while 5″ vacuum is ideal for vacuum instruments, they normally do well at 3″. So I did the cal and found that I could fly at 10-12k’ with about 4″ vacuum. Above that I would have to close the throttle a little to get 4″. I’m going on memory now- from the test I did 5 years ago, but I believe I had adequate vacuum (3″) at 12,000′ to run the two vacuum instruments. The vacuum is pulled from one side of the engine and affects those cylinders or that cylinder- not sure if one or two- more than the others. Bottom line is that it should work well at 7-8 k and probably at 12k as well. But, if you install one, do your own calibration for your aircraft. And, experiment with what vacuum is actually needed to give you reliable readings. If 3″, then set your own personal minimum- my instruments do o.k. at 3″ so I would adjust the throttle to give around 4″ if in IMC. I also have a G396 and its panel display would help make it a safe flight.

  • Blake Morrison