gallois wrote:
If on the other hand you are going to descend under full power, have you considered your maximum descent rate before you risk passing VNE?
Descent at any meaningful rate will be nearly impossible at full power. Bear in mind that Vne is for smooth air only. As you descend, you’re more likely to encounter turbulence on some days, and you really don’t want to get into turbulence when you’re already pushing Vne. Shock cooling should be considered. When you choose to shut down the engine, as you do, raise the nose as much as practical to reduce airspeed. Slowing the plane, slows the cooling, and reduces the effect of shock cooling.
Otherwise, shock cooling considered, glide from as high as you wish. You’ll find most GA planes very pleasant to glide, when you have time to settle in doing it. Of course, you practice forced approaches regularly, so a well planned forced landing should be a non event!
Peter wrote:
The engine is likely to run pretty unevenly if you pull the mixture back far enough to go from full throttle to say 30% of max power, at low level, but beggars can’t be choosers and you have to get back to the runway somehow
Right, but Arne wrote that in his case it was SOP according to the POH.
Pilot_DAR wrote:
Descent at any meaningful rate will be nearly impossible at full power. Bear in mind that Vne is for smooth air only. As you descend, you’re more likely to encounter turbulence on some days, and you really don’t want to get into turbulence when you’re already pushing Vne
Yes even in smooth air, I don’t think there is meaningful rate of decent to stay bellow VNE at full power in any aircraft: those with clean wings will have an excuse to go faster and those draggy have load of power to get there, obviously, none of them will do well in turbulence, also, as you descend on full throttle, a normally aspirated engine will tend to generate more HPs about +10% each 2000ft, so you are not even dissipating any energy and all forces now are pushing down, seems once above 2*VS0 on 100% power the only safe way for an aircraft is wing level and nose up
Depends on what climb you are trying to avoid? assuming you are high at 8000ft on full power, at cruise speed nose up means shallow climb, at about Vy = Vx =100kts I get best climb, at about 70kts with 1/2 flaps down it flies level on full power nose up (bellow that you get decent rate, stall warner horns and you are close to a spin, so not very good neither without that extra hand to cut the mixture 
), I can stay like that until airport overhead if I need to? if I need to go down, steepest way to descend from 8000ft to 2000ft when near airport overhead are straight lines (about 1/4 gradient) with 60kts full flaps and zero power or steep turn orbits at VFE with full flaps (no idea how quickly one go down), personal preference: I prefer to store height by staying high & slow without power rather than fast & low with power
Maybe there are ways to get from 8000ft at cruise speed and join at 2000ft overhead at circuit speed while keeping full power all time? shallow straight line decent then steep climbs? steep turns?
My experimentation today in my C 150M (with a 48" pitch prop) shows that even a gentle descent at full power will overspeed the engine. However, closing the throttle just a little kept me below engine redline RPM. With a sideslip at 100 MPH, I was able to descent a few hundred feet per minute steadily. If I raised the nose a little, I could slow below 100 MPH, and extend flaps. With that, I was able to descend from 3000 feet cruising, and set myself up with 20 flap extended, on close final, without reducing power below 2700 RPM (not quite full throttle, but close). I could pick my place on final, and cut the power as I wished for a gliding landing.
On the way home, in a slight climb, at full power, I pitched up fairly rapidly to slow. Once slower than 100 MPH, I extended 30 flap, and allowed the plane to slow more while climbing a little. Once slowed to 60 MPH, I entered a full sideslip again, and still at full power, was able to descend steadily at 400 FPM. Again, I could have positioned myself as I needed on final, and pulled the mixture for a gliding landing. It’s not a smooth ride, and very long sideslips probably don’t do the airframe a lot of good, but if it gets you where you need to be to make a good forced landing onto a runway, it’s worth it!
In accordance with my normal practice, I arrived over home with the power reduced, pulled to idle crossing over my house at about 1000 feet, and glided to touchdown. I was 150 feet long today, so I need a bit more practice. Though I’m a little un-nerved now, as my neighbour plowed her farm field, which abuts my runway, so undershooting would end really badly! So, I’ll allow myself the slight overshoot of my aim point!
My recurrent training is done for a while!
@Pilot_DAR would you agree that your method of descending full power and then a power off landing is both skilled and complicated? If so surely instructors need to at least pass on some of this skill during PPL training especially as the default to full power is as likely on most school aircraft as total loss of power. Secondly, sidelipping seems to have disappeared from PPL teaching since schools stopped using tailwheel aircraft and with the addition of flaps.
@Ibra are you sure you can get below VFE with full power and no significant climb at 5000 ft?
" do you make a "panne"call or just tell ATC your intentions?"
If I’m not going to follow normal procedure, I’d make a “PanPan” with explanation and intentions. For any problem.
I’ve done it once in 33 years.
gallois wrote:
Secondly, sidelipping seems to have disappeared from PPL teaching since schools stopped using tailwheel aircraft and with the addition of flaps.
My FI demonstrated the technique to me during my PPL training (2016), but I never used it on my own.
gallois wrote:
@Pilot_DAR would you agree that your method of descending full power and then a power off landing is both skilled and complicated?
Well… I don’t want to sound at all disagreeable, but the only thing unusual is that I did it (prompted by this thread, and that I sideslipped to accomplish it. It required a little attention, but I’ve done things in that plane a lot more demanding of skill than that!
gallois wrote:
Secondly, sidelipping seems to have disappeared from PPL teaching
Who’s the client? If you, as the student, want to learn what the plane does, you should ask, and the instructor should demonstrate. Oh… the instructor doesn’t know? That’s a problem! Yes… During design approval test flights I have flown, where and instructor, or company pilot came along, commonly, a sideslip is an “oh my god, you’re going to do what!?!” It should not be so. A sideslip is a very useful (as I demonstrated today), and benign maneuver. It’s a little more tender on some 172s, due to the dorsal fin arrangement, but still only an “avoid” rather than “prohibited”. Test pilot note: Were it to be worthy of prohibition, the plane would not get certified. Sideslips are a design requirement which must be demonstrated. Indeed, when I was asked to test fly a modified Cessna Grand Caravan last December, one of the maneuvers required to be demonstrated was I had to fly to the stall break, at a 30 degree angle of bank, at 75% power, and full rudder (sideslip) at the point of stall break. If the plane was uncontrollable, the mod would not have been certified. The plane did it just fine… That, did demand beyond PPL skill.
So, the plane will do it, so should your instructor – that’s what you’re paying for! Training!
Just now, I returned from two flights for fire patrol over a forest fire in my 150. As I was quite high, and very close to home, it was appropriate for practice forced approaches into my runway (2100′ × 40′). I had not been happy enough with my PFL this morning, my flare was stretched so as to use 1000 feet of runway to stop. Both power off (from 2000 feet AGL) landings this evening were down and turned around in less than 600 feet – I’m good with that. Both were very steep approaches for safety, with full sideslips most of the way down, flaps coming down when I knew I had the runway made. Once stable in a sideslip, the [steeper than normal] approach is also stable. get the approach about right with full rudder held in, start to extend the flaps as desired to tighten up the touchdown point, and if you have misjudged, unslip, your nice glide will instantly return.
In both power off landings, I held the slip into the flare, straightening out when one mainwheel touched. Happily, a sideslip is the easiest thing to practice – because you can start way up high, and get the feel of it, you can apply just a little rudder to get started, and it can be instantly undone! The main reason that sideslipping was so popular back in the ragwing taildragger days, is that most of the basic GA planes did not have flaps, so sideslipping was the only way to modulate a power off approach!
Training how to handle a surprise full power, loss of throttle control is not really vital, it’s a rare occurance. However, training the basics of sideslipping is vital, so the pilot has confidence to handle an unusual event.
