A report on REXFFA got me wondering why we are never really trained for the opposite to power loss in cruise.
The report referred to an instructor and student on a flight in a mountainous/hilly area. The climb was to 5000 feet because of the MSA. When the student levelled out and tried to reduce power the action on the throttle did nothing.
The report went on to say how one could only make a shallow descent without going over VNE etc.
All turned out okay but the conclusions pointed out that there are many aircraft that default to full power in the event of eg a throttle cable snapping. This was what happened on this Robin 400, although there is a mod to make it less likely as is used on PA28’s.
The conclusion went on to ask the question I have asked in this post,“how many pilots are trained to deal with such an event, even when it is possibly as likely as a loss of power in the cruise?”
At least you can turn an excess power incident into a loss of power incident by cutting of fuel or turn off the ignition. And for the latter we get trained. In some engine installations full power is even intentional in case of a broken throttle cable.
Of course, a real runaway can happen with a diesel engine (Google for impressive videos).
Indeed, I’d rather have excess power than loss of power, so the design of many engines to behave that way when the throttle cable breaks or the like makes sense to me.
It’s a matter of flying to the nearest airfield and cut the engine overhead or so. VMC would help a bit..
Upon realizing that you can’t reduce power, gently begin an ascending turn, As you slow toward slow flight, the turn may be reduced. Eventually, you’ll be in slow flight, full power, barely climbing, and flying straight, while you figure out what you want to do next. You can fly that way for a while, though overheating may be a risk. When you’ve found a suitable forced landing area (hopefully a nice runway), shut it down with mixture or fuel off. If you have to do this, it is really hard on the engine. Do you best to not accelerate too much as you start down, so the engine may cool gently, ‘no point shock cooling it. Then a nice power off landing, which I’m sure everyone practices regularly….
A very steep turn can also be use to absorb too much power, or a nose up runaway trim situation, while you figure it out.
One way to deal with excess power at wide-open throttle is to lean the mixture way beyond the peak and then use the mixture knob to control RPM. So long as the engine is running below 75% power, no amount of leaning would damage it.
I think there is no way to descend & position for landing on full power without being on the edge? only stable ways of flying on full power are climb when one is fast cruise to slow in climb (+shallow turns) or descent when one is slow cruise to accelerate in decent (+shallow turns)
I am disregarding steep 70deg 3G turns on full power, let’s say you can’t enter them on full power from level flight that easily…
On max power setting you can fly straight and level on two speeds: very fast cruise and very slow flight, at max power the former is near VNE an put you near spiral dives with highly sensitive controls and the latter is near VS0 and put you near spins, I personally, will go for one or the other depending on wind, turbulence and visual conditions? and how far from the airport?
- Sunny sky 10km visibility, clam air in flight level headwinds: fly level at 180kts clean on full power, pitch up to slow down & climb, pitch down kills you
- MVFR/IMC bumpy conditions close to airport no winds: fly level at 60kts dirty on full power, pitch down to accelerate & climb, pitch up kills you
3000ft overhead the airport I will cut fuel irrespective of conditions, how to switch between the two flying mode? climb 15deg turn from fast to slow as @Pilot_DAR suggested (try descending 15deg turn from slow to fast work) and cut power off sets you for best glide flying mode
Also thinking about deep LOP mixture to set 40% partial power for landing? but I may have max 5min of flying before fumes comes out?
Stuck throttle (it reverts to full power in the event of a throttle linkage detachment) is a regular emergency drill taught and practiced in my military school. Teaching is to recover either via a practice forced landing pattern from 3000ft overhead, retarding mixture in the overhead, or to run in one runway centreline at 400ft and retard mixture and pitch up to reduce speed and select flap when assured of the runway. In both cases a decentlength runway should be selected rather than home base if required.
@Pilot_DAR, might we also turn off one magneto, which has an effect equivalent to retarding ignition timing?
And maybe add carb heat?
Should we also increase propeller pitch/reduce RPM, if it is controllable?
Switching one mag off is decent trick to taxi very slowly on the water, when idle is still too much. It’ will have little effect in reducing from full power, similar to carb heat. You can play with propeller pitch, but again, it’ll have little effect in reducing power within the range of limiting engine RPM, and damaging over square operation. Leaning the mixture toward peak lean on an engine which is running at full power, is going to damage the engine well out proportion to controlling the power at less than full. You’ll find that at high power once you’re behind peak lean, the adjustment of the mixture is hyper critical to the point where the engine will stop. It’ll be a lot of effort to make any useful reduction in power without making the engine falter, and complicating your flight more.
Presuming that you are not bound by a ceiling (cloud or airspace), one could presume that gaining some altitude while slowing into slow flight would not be a problem. Very few airplanes will exceed Vne at full power, so you should expect to fly reasonably normally to an airport suitable for landing, it’s just managing the power once you want to begin your descent. If you’re hurtling along at high cruise speed, stuck at full power, slowing down aerodynamically as you stop the engine would be kind to it, and thereafter, slowing the plane more, rather than diving down. Shock cooling is a risk.
I would avoid extending any flaps while the engine is running (presuming you could slow it to flaps speed with full power). Once the engine has stopped, and you’ve entered a glide, you’d rather not have any drag flap out yet, extend the flaps when you need them.
My immediate thought would be to head back towards the airfield or suitable place, if you can climb high enough to get your manifold pressure right down. Head until you’re over somewhere that you want to land, then pull the mixture back very aggressively and (if you’re able to run deep lop keep it running with the power set by the mixture) If not just keep the power down and descend under power. I guess for a bit of control coming into land if needed you could use the mag switches if working to set power similar to the very early aero engines which throttled by just blocking spark.
