Simulation of suction failure

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TJ1376
Airman First Class
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Joined: 21 Dec 2014, 17:43

Simulation of suction failure

Post by TJ1376 »

Will the 172 simulate the spin down of the gyros as suction is lost? I was simulating a vacuum pump failure today (IRL) and placed suction cups over the attitude and heading indicator. However, in reading about this type of failure post flight, it appears that the instruments will actually read less accurately as the gyros spin down, getting progressively worse as the gyros slow.

So my question would be, can we simulate this? Is there a way to simulate poor vacuum pump performance that would keep the gyros spinning but not fast enough to be accurate? If it matters, I use p3d.

Appreciate any input.

TJ


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Oracle427
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Re: Simulation of suction failure

Post by Oracle427 »

For reference, this is what an AI instrument failure might look like. I once had my standby AI fail like this video shows below. Amusing unless you are in the soup!!!

https://www.youtube.com/watch?v=25JVFIX2Cvc
Flight Simmer since 1983. PP ASEL IR Tailwheel
N28021 1979 Super Viking 17-30A

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AKar
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Re: Simulation of suction failure

Post by AKar »

TJ1376 wrote:Will the 172 simulate the spin down of the gyros as suction is lost? I was simulating a vacuum pump failure today (IRL) and placed suction cups over the attitude and heading indicator.
Not sure what you attempted and on which model, but to simulate a vacuum failure, you'd probably want to put a small plastic bag or similar over to the gyro filter which is found up in the leg space. That way the vacuum pump would suck mostly through the regulator valve, meaning some insignificant flow and therefore poor spin of the gyros downstream from there. (Attempt on your own risk, of course! :mrgreen:) I wonder if any through-the-instrument suction schemes without a common gyro filter are around?

Edit: what's good to know, and a great safety feature in many airplanes using a rate-based autopilot is that the AP typically uses only the electrically powered rate gyro data from turn coordinator, and often it's own static pressure data. It doesn't know nor does it care about the airplane's indicated attitude, only about it's rate of turn. In case of loss of the attitude indication, it would make a nice timeout to figure out one's bearings.

-Esa

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