NewbRVator
Well Known Member
Knowing HOW to do a turn back is probably just as important as knowing WHEN to do a turn back certainly not greater given in many if not most engine outs on takeoff straight ahead is probably preferred. BWTHDIK
Knowing HOW to do a turn back is probably just as important as knowing WHEN to do a turn back certainly not greater given in many if not most engine outs on takeoff straight ahead is probably preferred. BWTHDIK
About 8 years ago I wrote an article on this topic, advocating takeoff briefings for single engine aircraft:
https://www.rapp.org/archives/2014/08/takeoff-briefings/
--Ron
Starting to appreciate my training a bit more. It's pretty settled science that getting important stuff into your "working memory" can greatly increase performance.There has been at least one EAA safety webinar that recommended performing a pre-takeoff briefing, specifically for the engine out scenario at takeoff, even for a local flight. I don't know any basic flight training that teaches this, maybe except for the commercial/corporate/airline world
There has been at least one EAA safety webinar that recommended performing a pre-takeoff briefing, specifically for the engine out scenario at takeoff, even for a local flight. I don't know any basic flight training that teaches this, maybe except for the commercial/corporate/airline world
I can tell you that at the soaring school where I got my glider rating, failure to verbalize the pre-flight briefing before signaling the tow plane to go ensured that you’d have a 200’ rope brake, courtesy of the instructor in the back seat.
Vince, sound methodology. Thanks for sharing results.
Low altitude maneuvering is an energy/AOA management problem. There is an optimum AOA for approach and landing that is coincident with maximum sustained turn rate. In the military, we called this an ONSPEED condition. If an aircraft is ONSPEED, energy “burn” and turn performance are optimum. It’s also usable trade-off between maximum duration and range glide (max endurance glide occurs ONSPEED flaps up, and as flaps are deployed, L/Dmax and ONSPEED marry up), so it’s a simple single reference to fly to the crash if there is a loss of power:
https://youtu.be/LT6OSNblXpc
Notes, warnings and cautions: I’m not advocating any specific course of action in the event of engine failure except to maintain aircraft control—this is a discussion forum, not a flight training institution. The video is a demonstration of using a calibrated AOA/energy cue as a primary reference, which is something we did in the military. Since I’m flying AOA as my primary reference, bank angle is “whatever it takes.” I wouldn’t attempt this without accurate, easy to use AOA cuing. The steady tone tells me the airplane is in an ONSPEED condition. I adjust AOA based on the tone. This is a test, so there is no startle factor. I allow three seconds after simulated power loss prior to maneuvering. The airplane has a fixed pitch propeller, so there is some residual thrust at idle. Performance would also be different with a controllable pitch propeller, depending on RPM. Field elevation is 250’ MSL. In this test, the throttle is pulled to IDLE at 250’ AGL at L/Dmax AOA during initial climb segment. Flaps 20 is selected for the turn back (best compromise for lift benefit vs drag with my 2-position manual flaps at low altitude). See post 31 for links to additional technical resources if you are joining the discussion late.
Fly safe,
Vac
FlyONSPEED.org
As a sea going Marine I cut my teeth on AoA vs Airspeeds for all flight regimes except maneuvering speed and runway numbers for obvious reasons. So when I went GA I always wondered why floating airspeed references were vogue for things like cruise, stall, climb and endurance.
But there certainly is a strong desire to focus on airspeed in GA, I get that.
What Vac is trying valiantly to do is to get a paradigm shift toward AoA.
A spin entry at anything below spin recovery altitude plus change is to be avoided at all costs. We can't do that with airspeed but we can do that with AoA and proper feet control. Spin entry requires excessive AoA and asymmetric loading. If AoA and coordination are managed a spin is impossible, I say again impossible. I would even go as far as to say that if AoA OR coordination are managed a spin is avoided. But safer to keep both under control.
So a gentle 20 deg AoB in the pattern at O/S AoA presents the same aerodynamic risk as 45 deg AoB at O/S AoA. In fact the 45 deg bank at O/S AoA preserves more kinetic energy so one could argue it is even safer.
Power out: There are reasonable bugaboos out there for pulling the fuel out of the engine while airborne. Thought must be given to thermodynamic changes, but that's manageable inflight and doesn't need to be any more extreme than an ordinary shutdown. I personally don't think using the full range of the mixture knob is any more dangerous than using a partial range but that is just me. Everybody who agrees to fully test their experimental aircraft and determine their true operational performance envelopes (Phase 1) must wrestle with the decision to go there. But I do believe we each must know our real glide numbers straight ahead and in turns. Imagine if our trusty 152 glide numbers were given to us by the factory as a best guess.
My point is that we shouldn't confuse a risk of spin entry with managed AoA.
Vince, sound methodology. Thanks for sharing results.
Low altitude maneuvering is an energy/AOA management problem. There is an optimum AOA for approach and landing that is coincident with maximum sustained turn rate. In the military, we called this an ONSPEED condition. If an aircraft is ONSPEED, energy “burn” and turn performance are optimum. It’s also usable trade-off between maximum duration and range glide (max endurance glide occurs ONSPEED flaps up, and as flaps are deployed, L/Dmax and ONSPEED marry up), so it’s a simple single reference to fly to the crash if there is a loss of power:
https://youtu.be/LT6OSNblXpc
Notes, warnings and cautions: I’m not advocating any specific course of action in the event of engine failure except to maintain aircraft control—this is a discussion forum, not a flight training institution. The video is a demonstration of using a calibrated AOA/energy cue as a primary reference, which is something we did in the military. Since I’m flying AOA as my primary reference, bank angle is “whatever it takes.” I wouldn’t attempt this without accurate, easy to use AOA cuing. The steady tone tells me the airplane is in an ONSPEED condition. I adjust AOA based on the tone. This is a test, so there is no startle factor. I allow three seconds after simulated power loss prior to maneuvering. The airplane has a fixed pitch propeller, so there is some residual thrust at idle. Performance would also be different with a controllable pitch propeller, depending on RPM. Field elevation is 250’ MSL. In this test, the throttle is pulled to IDLE at 250’ AGL at L/Dmax AOA during initial climb segment. Flaps 20 is selected for the turn back (best compromise for lift benefit vs drag with my 2-position manual flaps at low altitude). See post 31 for links to additional technical resources if you are joining the discussion late.
Fly safe,
Vac
FlyONSPEED.org
The Onspeed device works for our EAB, Vans, but for most of the training fleet comprised of older 172 and Cherokee, the OnSpeed device and precise AoA measurement aren't available. So the GA fleet relies on the power settings and reference speeds. I think this method has worked well for the GA, especially for teaching new pilots.
I think I've got this right, somebody chime in if you see a logical error.
In previous posts I laid out that my RV-7 and I have been tested and we need 650' at a DA of around 6000' to execute a 90-270 turn. In those same conditions on takeoff we covered 7,900' to go from stop to 650' AGL. I calculate that we make about 900' distance toward the runway in the turn.
Note that this discussion is assuming a straight out departure.
So theoretically on a 7000' runway I can make the threshold from 650' AGL in a DA 6000' or less.
But what if the runway is shorter? I'll finish the turn but well short of runway.
Comparing my 7:1 climb ratio beginning at 7,900' from the brakes release point at 650' AGL, with my 11:1 glide I come up with needing an extra 250' AGL for each 1000' increment of runway length less than 7000'
Example: Take off from a 3000' runway. At 650 I can execute a turnaround but will be 4000' short of the opposite runway threshold. I still need about 400' AGL once I finish the turn to glide the rest of the way. So the added numbers look like this: 4(k) * 250' +650' = 1650' AGL required to execute a turnaround and expect to make the threshold of a 3000' runway. Why so high? Because I'll be 2.7 SM from the threshold once I finish the turn around, and those are the numbers required to glide to make concrete.
If it's rural and there is plowed field then a turn around from less than that may be smart. But if it's warehouses at the departure end then it's 1650' AGL or forget about the runway.
To me that is a shocking bit of information! Surely 1,500' AGL is enough to turn back right? Not according to the math if the runway is typical for an RV.
My testing was done in the vein of normal operations. My takeoff wasn't max performance, it was a normal takeoff. My turns weren't practiced extensively, they were done with moderate proficiency. Surely the climb and turn numbers could be tightened up, but these represent what I will likely encounter in an unexpected loss of power on takeoff. Also there will be extra energy remaining the further you get from the runway and the more you can round off that 90-270 into more of a 15-195.
Good argument for VCOA
Food for thought.
Good points. He also got slow in the turn and said in his narration he had to tell himself to push the nose down. That is where pilots FAIL and sadly stall and spin. Pilots close to the ground don't want to push the nose down and fly into a crash, and add task saturation a stall often occurs. I just completed my CFI renewal (15th renewal over 30 yrs) and there was much discussion in the renewal course work about turn backs, LOC (loss of control) and accident statistics.. The statistics show fatalities go way up if turn backs are made below 800 ft. Success rates although not 100% for turn backs at 800 ft or higher, did have lower fatalities.[snip] I am posting this because I learned a lot from watching this video because a lot of things went right with this emergency landing. There are a lot of video angles from this airplane, from the cockpit view to the outside view.
Airplane: Cessna Turbo Centurion. (Retractable gear. Gear retracted at take off and redeployed during the emergency landing)
Test Condition: 1st test flight after engine overhaul (remember what Mike Busch said about engine overhaul.) He blew a rod through the case. The data plate held the case together.
Pilot: He is fully aware that he may have engine problem before the flight and was prepared to land when he encountered the engine failure. I don't think he expected his newly overhauled engine to hand grenade, but agree he was on guard. He reacted quickly lowering nose and turning left (which was the best direction). He narrates I know you are not suppose to turn back.
Landing: Landing was not on the same runway. The intersection runway was used and it meant he didn't turn as much if he had to land on the runway he took off from. This saved the day. He departed Rwy 30 and landed Rwy 08. If he had to land on same runway Rwy 12, another 40 degree turn would have had him end up short of runway. He landed ON the threshold of the runway (with overrun).
Picture of the flight track via ForeFlight.
https://youtu.be/9FdRQiHyWQs?t=307
I want to add to this thread about an actual successful impossible turn with an engine failure. While this is not a RV specific airplane, I am posting this because I learned a lot from watching this video because a lot of things went right with this emergency landing. There are a lot of video angles from this airplane, from the cockpit view to the outside view.
Airplane: Cessna Turbo Centurion. (Retractable gear. Gear retracted at take off and redeployed during the emergency landing)
Test Condition: 1st test flight after engine overhaul (remember what Mike Busch said about engine overhaul.)
Pilot: He is fully aware that he may have engine problem before the flight and was prepared to land when he encountered the engine failure
Landing: Landing was not on the same runway. The intersection runway was used and it meant he didn't turn as much if he had to land on the runway he took off from.
Picture of the flight track via ForeFlight.
The take off starts at 5 mins mark.
https://youtu.be/9FdRQiHyWQs?t=307
The way to optimize the turn back is to pull as close as you can to stall without stalling. Of course that is dangerous bordering on insane but that’s what the math says works. Lift is everything and drag is secondary. So unless you pull aggressively you aren’t going to make it. Im not sure what technique was being used in these tests.
Finally someone who understands what I have been saying for a long time. In addition if you are in a side by side aircraft, in non crosswind conditions, immediately offset to the right (terrain permitting) so you will be able to keep the runway in sight on the left side in a climb.You don't need to fly on the edge of a stall to make it from 500' in a RV-4. Engine out I aim for 90 mph, 45 degrees of bank or so. You can make your job easier by always setting up for a turn back by offsetting down wind (let any crosswind blow you off the center line once a rejected take-off is not an option).
Fly coordinated (no skids near the ground). Start your practice at 1,000 AGL and gradually work down to see what you are comfortable with.
.... Wind will play an effect on this too but don’t think you can glide farther just because you’re light.
Good to see someone who understands weight. Weight won't matter much, especially for the two seat and single seat EAB. In a jet airliner say in the 110k max gross weight range, max landing weight approximately 99k, weight with crew and min fuel 65k: At max landing weight the airplane from 30'000' to sea level will typically travel 90 nm in high speed descent. At minimum weight approximately 60 nm. Idle power, 300 kts indicated to 10'000' and then 250. Same principle in glider except the glider pilot plays a guessing game with lift. Heavier weight reduces rate of climb but increases glide performance.Thinking about weight. When flying glider, I get the better glide with more ballast. Given the low glide ratio of these short winged powered airplanes, the gliding distance won't be a factor. The speed will be higher for higher weight though, and it means higher energy at touchdown.
There are exceptions.There are people who discuss the turnback as a 90/270 turn. Charlie Precourt in Sport Aviation series on the subject states a minimum of 190 to 210 degrees of turn. The 90/270 has no place in this discussion UNLESS very unusual high terrain or obstruction is involved almost at the departure end of the runway.
Interesting discussion and there may be some misconceptions. All things being equal, weight is not going to change the glide distance. You may have to change speed to compensate for a heavier aircraft and you won’t have as much time to figure things out, but you will end up at the same place on the ground. Wind will play an effect on this too but don’t think you can glide farther just because you’re light.
For those who feel a 45 degree bank close to ground is suicidal perhaps they should choose another hobby.