10
$\begingroup$

There are a few aircraft, such as the Britten-Norman Trislander, that use three piston engines -- one on each wing and one mounted along the centerline somewhere.

This is fine and good, but how do you tell in a timely fashion that the #2 (centerline) engine has quit? The engine gauges are in no hurry to tell you, as per Randy Sohn's Warbird Notes #6, and there's no adverse yaw because it's a centerline-mounted engine, but you still need to know and quick because unless you can get that prop feathered, there's a giant drag bucket hanging off your vertical tail!

$\endgroup$
  • 6
    $\begingroup$ Perhaps the giant drag bucket hanging off your vertical tail will be a clue? $\endgroup$ – fooot Mar 19 '15 at 22:53
  • 1
    $\begingroup$ Wouldn't the lack of adverse yaw be a sign by itself? $\endgroup$ – cpast Mar 20 '15 at 3:33
  • 2
    $\begingroup$ Another issue is that on two engine a/c you might see a MAP difference, but still be unable to tell which engine still produces power, and which is windmilling. Having 3 sets of instruments makes it easier to spot the "odd" one in relation to the remaining two engines still producing power $\endgroup$ – Radu094 Mar 22 '15 at 16:00
9
$\begingroup$

If the engine quits you will lose some thrust which will affect the plane's handling. You may even begin to descend slowly which the pilot will notice.

Most importantly you have engine instruments which will tell you, quite quickly, the engine has quit. If you have one, your manifold pressure will drop since you are no longer producing power, or your tach will reflect what is happening.

If all that fails you I would think there would be an audible difference if the engine cut out.

This is the cockpit of the aircraft in question: enter image description here
(Image Source: Jetphotos.net)

It does show independent MAP and RPM gauges for each engine as opposed to some planes that have a single gauge with multiple hands (one for each engine). You would surely be able to see an altered reading on one of these gauges.

$\endgroup$
  • 1
    $\begingroup$ Interesting that you say that the engine instruments would pick up on it quickly -- is this a difference between radials and in-line/opposed reciprocating engines, or something to do with forced induction vs natural draft? $\endgroup$ – UnrecognizedFallingObject Mar 20 '15 at 0:17
  • 1
    $\begingroup$ I would think that in cruise flight you would have your gauges set, if the engine cut out, even if the gauges still had a reading it would likely not be your set cruise power. As a pilot you chose your cruise settings and should check your instruments routinely. Granted MAP shows suction so if you chose your MAP to be equal to the atmosphere at that level you may not see a difference if the engine cuts as the MAP will measure ambient pressure. $\endgroup$ – Dave Mar 20 '15 at 0:33
  • 3
    $\begingroup$ MP is not a measure of "power produced" per se, but an indication of the pressure in the intake manifold. For a normally aspirated engine, with the engine running, MP will be below ambient pressure because of the engine working as a vacuum pump. With an engine failure, (considering a constant speed prop), RPM will at "best" remain constant, or more likely decrease with the governor unable to maintain the same RPM. This means less suction out of the manifold. Conclusion: MP will NOT decrease from an engine failure (normally aspirated, constant speed propeller). If anything, it will increase. $\endgroup$ – Waked Mar 22 '15 at 19:10
  • 2
    $\begingroup$ Which instrument will quickly tell you which engine quit? The propellers are constant-speed units, so RPM won't. And in normally-aspirated engines, manifold pressure is a function of ambient pressure, RPM and throttle position, so MP won't either since non of those three changed. And I don't see anything else in the picture. $\endgroup$ – Jan Hudec Mar 23 '15 at 8:02
5
$\begingroup$

Without having flown this particular aircraft:

According to Wikipedia, the aircraft is powered by the, non-turbocharged, Lycoming O-540-E4C5. This means that in a climb for instance, where you'd likely be at full throttle with this engine, if an engine stops (seizes), its indicated Manifold Pressure (MP) will be near ambient pressure, just like the other, running engines will be (at least for practical purposes), if it windmills, the engine will still work as a vacuum pump out of the throttle manifold, maintaining a still reasonable MP-setting. As the propeller will be windmilling initially, RPM is likely to, at least initially, stay in the same ballpark as the other engines (anyone who's flown older light piston aircraft will tell you most engine instruments are not accurate enough to make exact comparisons by value between the engines, try for instance syncing the propellers by the RPM gauge, and not by your ears). Unless the aircraft is equipped with torque indicators (not likely), the first instrument you will clearly be able to identify the engine failure is likely going to be the Exhaust Gas Temperature (EGT, an instrument I'm not sure if this aircraft is equipped with).

In a climb, or high powered cruise, the aerodynamic/kinesthetic feedback of the aircraft will be significant enough if you lose 1 of 3 engines, (deceleration, loss of climb performance, torque, change in sound) to warrant further investigation (and with proper training/experience, rather quickly conclude an engine failure). In a low powered descent, an engine failure can be quite insidious even on a light twin, and you are actually not likely to detect it until you apply power to level out.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.