WHAT DO I DO AFTER I SAY "Oh, *@#%!!"?
Acknowledgements: Russ Erb/EAA Chapter1000
Remember those fun times while
learning to fly when you sadistic instructor reached over, pulled the throttle
to idle, and waited to see what you would do? And of course, just pushing the
throttle back up where it was, slapping your instructor's hand, and telling him
"Don't you ever do that again!" was not an acceptable solution. The
point was to force you to practice your response to a simulated
"emergency." Usually these types of emergencies are covered in the
Pilot's Operating Handbook, so I won't rehash them here. Other minor failures
are covered in your flight training, such as what to when your radio fails. In
fact, most aircraft (if not all) can be safely landed in VMC with a total
avionics failure.
Learning to fly is a process of
learning to manipulate various controls in the cockpit. We assume that these
controls will always work as expected, but what do you do when they don't? The following thoughts have not been endorsed
by the FAA or your airplane manufacturer, and are presented without prejudice to
help you determine your own procedures in the comfort of wherever you
are now, rather than when you're plunging earthward with no clue what to do.
You will probably notice this problem when you try to lean the engine
for cruise and the mixture lever gets all the way back to idle cut-off with no
increase in EGT and no decrease in RPM. This could be caused by a break in the
cable. If the break is in the middle of the cable, you may be able to move the
mixture to full rich by pushing in on the control, but not to lean the engine.
This is okay, since most aircraft land at full rich anyway. If the break is at
the cockpit end of the cable, you may be able to grab the cable and move it
without the lever. By the time you find out about this problem, you will
probably not know where the mixture control at the carburettor is set. There
are three likely possibilities, which could change from one to another at any point:
1) The mixture control has leaned to idle cut-off.
The sudden quiet and the propeller logo should be your first clue on this one!
Institute engine-out procedures
2) The mixture control is at full rich. This is not a big problem, since this is where you normally want it
for landing, but remember that you will have a higher than normal cruise fuel
flow, and there may also be a reduction of power to compensate for.
3) The mixture control is still where you last
leaned to. OK as long as you stay at or
above the altitude where you last leaned the engine, but when you descend there
is a chance that your engine will become over-leaned by the increasing air
density, possibly causing over-heating or engine stoppage. So, plan a higher
than normal approach, such that you will still be able to make the runway even
if the engine quits at any point. Applying full carburettor heat will also
enrichen the mixture.
After a successful landing, you can stop the engine by turning off the
mags, but remember that the engine may continue to run for a while, and there
will still be fuel in the engine.
If you have a fixed pitch propeller, skip this section. If your flight manual has a recommended
procedure for this emergency, follow it. The cause of this problem could be a broken cable, or a malfunction in the propeller. Either
way, the result to you is the same - you have no control over propeller RPM. Again,
if this happens one of three situations are likely, and can change at any time:
1) Runaway Prop (Over-speed).
The blades have decreased in pitch, and may have gone all the way to flat
pitch, and thus cannot produce the blade drag to offset the engine torque. The
immediate action required is to retard the throttle until the RPM is back
within limits. If the over-speed continues, the prop may shed a blade, followed
shortly by the engine and its unbalanced propeller. This is real BAD, since you
will now have a severe un-recoverable aft CG problem. Once
you have the RPM within limits, and if you can still maintain level flight,
decide whether to make for the next airport on your plan or the nearest
airport. Be alert, because your situation might get worse and you may have to
make a power off landing anyway. As before, make a high approach, ready at all
times to totally lose all thrust.
2) The prop is stuck at its
last setting. This is OK as long as the RPM doesn't change. Try to increase the
RPM to the landing RPM, as the push-pull cable may still push but not pull. If
you cannot increase the RPM, you can fly the approach at cruise RPM, but remember
you may not be able to go-around, so avoid as much as possible any need to.
Plan the high approach, alert for engine failure at any time.
3) The prop feathers or
partially feathers. The blades have increased in pitch, and the RPM drops. If
prop RPM cannot be increased, check if there is enough thrust for level flight.
If not, look around for that landing spot and follow your loss of engine power
emergency procedures. If you can maintain level flight, follow the same
approach procedures detailed above.
Another possible case of a broken cable. You may be able to increase the
throttle but not retard it if your push-pull cable has become just a push
cable. If the engine goes to idle, it's engine out landing time. If the engine stays
at cruise power or higher, you should be
okay until time to make the approach. Of course, it could change to idle at any
time, so be ready for that engine out landing. For the approach, you can
descend at higher than normal speed, but be careful you don't
exceed your aircraft's speed restrictions.
Eventually you will need to slow down. You can by over-leaning with the
mixture control, but this is pretty much an all or nothing proposition. Don't
pull it all the way back to idle cut-off, or you'll be staring at that propeller
logo! Don't cut off the mags if you don't have to, because once the engine
stops, you may never get it going again. The engine may start to overheat if
leaned for too long, but this will probably be the least of your worries at
this point.
The cable to the elevators snaps, or the push-pull rod breaks. As long
as the elevator doesn't get stuck in a hard over position, you have a decent
chance of getting down in one piece. If the pitch
trim still works, make small inputs and think well ahead, since this method
of pitch control is not as responsive as the yoke. If the pitch trim isn't
working, you may be able to control your pitch trim with the flaps. The throttle can also be used to an extent to control pitch, but the drawback is that
if this is your only method, you probably won't be able to slow to landing
speed. You'll be stuck with a Navy landing of flying the airplane into the
ground (hopefully at a very shallow angle)! In any case, plan a shallow,
stabilised straight-in approach, with minimal manoeuvring required. Remember
that the pitch change to flare is significant, so be ready for it but be careful
not to over-flare. If you do, go-around and try it again.
This is not really a big problem, as long as one or the other is still
functional. If the ailerons are
working, ignore the ball and make uncoordinated turns. If the rudder is working, simply roll with the rudder (rudder turns). Look for a
runway with little to no crosswind, since you won't be able to slip (wing-low
method) without both controls. Consider flying in a crab all the way to the
runway if necessary. Also look for a straight-in approach with minimal manoeuvring.
Total
loss of flap control is not too serious. Simply make a no flap landing, which
will no doubt be faster and shallower than normal. Split
flaps (one flap lowered more than the other) can be very bad, as you may not
have enough aileron control to overcome the rolling moment. If, while moving
the flaps, you notice an un-commanded roll, stop the roll if possible with the
ailerons, and move the flaps back to their original position before the
problem. If they were up, put them up. If they were down, put them down. Leave
the flaps there, and proceed with the landing as appropriate for the flap
position.
This article is intended to get you thinking about possible failure
modes in your aircraft that are not covered in your Pilot's Operating Handbook.
Consider each system on your aircraft and ask yourself "What would I do if
this failed." These areas should be checked regularly to minimize the risk
of such a thing happening. It's better to think about it while safely on the
ground rather than after the failure occurs. At that point, it may be too late.
FLY SAFE!