Using rudder to turn

[ahramin]

Excerpts from a recent Bits and Pieces article.

I pushed the throttle to full power and began the takeoff roll, and it all was so darned normal until I got airborne. The engine began to miss, cough, catch, sputter, et cetera, and we weren't climbing. If this has ever happened to you, you know it is not a good thing. I was able to maintain about 300 feet and minimum flying speed with the engine alternately surging and quitting. I managed to complete the never-to-be done turn back to the departure runway by using rudder only to flat turn, avoiding any stall-increasing bank.

It's interesting that earlier in the article he mentions using a slip to get rid of extra energy

I set up for final approach and then had to slip off a lot of extra height.

but doesn't seem to understand that skidding an aircraft around a turn when you are low on energy is more likely to lead to a stall. I remember during my commercial meeting a lot of instructors that didn't understand that an airplane at 1G stalls at the same airspeed regardless of bank angle. It seems that the fundamentals of why stall speed increases in a bank is often not understood, leading to problems like that illustrated above.

[Flight94]

Using the rudder to push the nose around is a technique used by ag pilots in a low energy/high bank angle (90 degree bank or greater) scenario. If the nose is falling through the turn, the aircraft cannot stall. The wings are also brought back to level using rudder to pull out of the dive. Using aileron in a low energy state is what can aggravate or initiate a stall.

In a 300' engine failure, yes, absolutely use rudder to push the nose around to the desired target. BUT THE NOSE MUST BE ALLOWED TO FALL THROUGH THE TURN!! That's the difference.

Read "Contact Flying" by Jim Dulin, and the energy management turn is explained in detail. It is somewhat contradictory to what is taught.

Good topic for discussion though regardless of your views.

[Flight94]

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[ahramin]

Flight94 it sounds like you are talking about using the rudder to roll the aircraft. Not sure why that would be better than a coordinated roll but in the above case it sounds like the author was using the rudder to yaw the aircraft while keeping the wings level with aileron. I might be wrong about that though, the aircraft was a citabria and I'm not sure how much roll you get from rudder input.

[digits_]

Excerpts from a recent Bits and Pieces article.

I pushed the throttle to full power and began the takeoff roll, and it all was so darned normal until I got airborne. The engine began to miss, cough, catch, sputter, et cetera, and we weren't climbing. If this has ever happened to you, you know it is not a good thing. I was able to maintain about 300 feet and minimum flying speed with the engine alternately surging and quitting. I managed to complete the never-to-be done turn back to the departure runway by using rudder only to flat turn, avoiding any stall-increasing bank.

It's interesting that earlier in the article he mentions using a slip to get rid of extra energy

I set up for final approach and then had to slip off a lot of extra height.

but doesn't seem to understand that skidding an aircraft around a turn when you are low on energy is more likely to lead to a stall. I remember during my commercial meeting a lot of instructors that didn't understand that an airplane at 1G stalls at the same airspeed regardless of bank angle. It seems that the fundamentals of why stall speed increases in a bank is often not understood, leading to problems like that illustrated above.

It wouldn't just be a stall, it would be a nasty wing drop as well in most planes. Weird how he seems to be patting himself on the back for such a brilliant technique...

[photofly]

I don't think thinking about "stall speed" is helpful.

An aircraft genuinely on the edge of a stall in level flight with no excess power available will be unable to turn using either method, without descending. Everyone understands that a banked turn requires extra lift to maintain altitude: either the aircraft descends or the pilot increases the coefficient of lift (by increasing the AoA) to increase lift. If already on the edge of a stall, that cannot be achieved.

However by turning in a flat attitude, extra drag is created because the sideways force to move in a curved path is created by airflow across the fuselage, i.e. a sideslip angle. This is a very inefficient way to turn. That extra drag would cause the putative aircraft to slow down and therefore descend. A pilot who tried to maintain altitude by pulling back on the yoke would stall.


Generating the sideways force to turn by diverting the lift from the wing, increasing that lift, and accepting the small drag penalty of that increase, is the most efficient way of doing it: that's why we use it. As you can see from elementary trigonometry, a small sideways force requires almost no extra lift at all, and therefore almost no extra drag, when you tilt the wing a little bit.



I suspect that for whatever rate of turn the pilot managed to generate in his flat turn, it would still have been more efficient in terms of height lost to have used a gentle bank to get that same rate of turn in a coordinated fashion. The increase in AoA required to maintain level flight in a gentle bank is very small, and so is the extra drag.

That he didn't lose height in a flat turn tells me that he could better have used a gentle banked turn to the same end.



I have used a number of skidding turns, at a sensible airspeed - they're very helpful to orbit a building site when the guy on the left is taking aerial photos, and a banked turn would put the wing-tip into shot. You do not of necessity stall, spin, or die. You do however need to keep the airspeed up, and the drag is high, so you need a lot of excess power.

[Big Pistons Forever]

I pushed the throttle to full power and began the takeoff roll, and it all was so darned normal until I got airborne. The engine began to miss, cough, catch, sputter, et cetera, and we weren't climbing. If this has ever happened to you, you know it is not a good thing. I was able to maintain about 300 feet and minimum flying speed with the engine alternately surging and quitting. I managed to complete the never-to-be done turn back to the departure runway by using rudder only to flat turn, avoiding any stall-increasing bank.

Personally I think we are having the wrong discussion here. As TC has reported turnbacks are 8 times more likely to result in a fatal accident than just crashing straight ahead under control. At 300 ft you should have as a result of a mental takeoff emergency brief already be primed to just push the nose down pull the throttle all the way back and ride it out straight ahead.

The second important point is that partial engine failures are more common than a total loss of power but are actually much harder to handle because of the ambiguity. It appears to me that the only reason that this person survived the turn back is that there was enough power being generated to keep the aircraft flying as it turned. If the partial power failure had turned into a full power failure half way around the turn I am sure it would have ended very badly.

With respect to skidding turns there are a few specialized applications where it can be used, for instance I have used a skid to reduce my turning diameter when trying to thermal in a very narrow thermal when gliding but as a general rule it should never be used at low altitude.

Finally it would be interesting to know why the plane lost power in the above example. The accident record clearly shows that approximately 80 % of loss of power incidents in GA piston engine aircraft are caused by the actions or inaction of the pilot. The best way to deal with a loss of power is to not have the engine fail in the first place.

[ahramin]

Finally it would be interesting to know why the plane lost power in the above example. The accident record clearly shows that approximately 80 % of loss of power incidents in GA piston engine aircraft are caused by the actions or inaction of the pilot. The best way to deal with a loss of power is to not have the engine fail in the first place.

Flying a borrowed aircraft. From the article:

Once on the ground, the engine ran normally. We taxied back to the hangar, and I tried several full power run-ups and everything seemed fine. I shut everything down and tried to figure out what had happened and why.

As I looked around the cabin, it soon became clear what the problem had been. There, under the left side of the panel, was a fuel valve firmly in the "off" position. It seemed very tight when I turned it on, but it did move, slowly. I restarted the engine and did another run-up and everything seemed to work fine. After convincing my very brave wife that everything was okay, we again took off and had a very enjoyable hour-long sightseeing trip.

Further investigation showed that the factory swivel connection at the fuel valve had been replaced by a homemade part sometime in the aircraft's history. The valve had become stiff, as they do with age, and this bogus fitting had bent. The bending, combined with the stiffness, resulted in the valve not shutting off completely. This allowed enough fuel for a run-up and taxiing, but not enough to sustain takeoff power. Had the valve shut off properly, the engine would have started but run out of fuel before I got to the run-up bay, thus alerting even me that something wasn't quite right.

Two previous owners had never used the fuel shut-off, and of course had never had a problem, as the valve was always full on. The current owner was in the habit of shutting off the fuel. He had previously owned a Champ and shut the fuel off after each flight due to a leak through the carburettor. I have never shut off the fuel in my Stinson and never even thought about the valve. However, had I taken the time to use the printed checklist stashed up high on the right side of the cabin, none of this would have happened.

[ahramin]

At 300 ft you should have as a result of a mental takeoff emergency brief already be primed to just push the nose down pull the throttle all the way back and ride it out straight ahead.

I dunno. At 300' with enough power to maintain power and airspeed I think I'd take the shortest turn to a runway. If it subsequently quits completely then sure, fly it to the ground but if there's enough power for a circuit, there's enough power for a circuit.

Of course, the above is predicated on a pilot being able to keep the airplane flying all the way to the ground. I keep harping on our club members that in the event of a power loss or performance loss it's perfectly acceptable to crash into anything they like, but it's completely unacceptable to stall at any altitude.

[photofly]

. At 300 ft you should have as a result of a mental takeoff emergency brief already be primed to just push the nose down pull the throttle all the way back and ride it out straight ahead.

I've never been a big fan of "go straight ahead, regardless"; the best thing to do rather depends on where you are. If you go straight ahead, regardless at CYTZ, you'll drown in the middle of the harbour or the middle of the Humber Bay, especially this time of year, while 300' is plenty of altitude with which to manoeuvre to ditch close to one of the beaches or docks.

If you go straight ahead at CYOO, you'll probably hit someone's house and kill them and/or their children, depending on the window of which bedroom you crash though. 300 feet is plenty of altitude to do at least a little manoeuvring, for one of the parks, or golf courses.

Most advice of the form of "in situation X, you should always do Y" can be bettered with a bit of thought.

[rookiepilot]

. At 300 ft you should have as a result of a mental takeoff emergency brief already be primed to just push the nose down pull the throttle all the way back and ride it out straight ahead.

I've never been a big fan of "go straight ahead, regardless"; the best thing to do rather depends on where you are. If you go straight ahead, regardless at CYTZ, you'll drown, especially this time of year, while 300' is plenty of altitude with which to manoeuvre to ditch close to one of the beaches or docks.

If you go straight ahead at CYOO, you'll probably hit someone's house and kill them and/or their children, depending on the window of which bedroom you crash though. 300 feet is plenty of altitude to do at least a little manoeuvring, for one of the parks, or golf courses.

Most advice of the form of "in situation X, you should always do Y" can be bettered with a bit of thought.

Off Rwy 15 (or 21) at buttonville isn't too nice, either, as a couple of unfortunate pilots have discovered.

Certainly makes one consider runway choice....when winds are light.

Even a very slight tailwind might be preferable, for better terrain....

[Big Pistons Forever]

I have to say my spiny senses really started tingling when I saw this

I was able to maintain about 300 feet and minimum flying speed with the engine alternately surging and quitting.

300 ft AGL with just enough power to maintain "minimum flying speed" and the pilot executes an approximately 225 deg turn to get back to the runway and then a turn back to line up

I think this pilot was very lucky that he made it. He was IMO one extra engine stumble from loosing flying speed while executing a level skidding turn . Stalling in this configuration will cause an instant spin entry and ground contact at a steep nose down pitch attitude and heavily banked. This combination is almost invariably fatal.

There was a study done by an Embry Riddle researcher who looked at the relationship between aircraft attitude at ground contact and fatalities. He looked at 10 years worth of US GA accident data. If the aircraft hit in control in a mostly wings level and level to moderate nose up attitude, only about 7 % had fatalities. This was for every kind of crash including , hitting bridges, buildings, trees water etc etc

However if the aircraft hit out of control and at a steep nose down attitude there was fatalities in 85 % of the accidents. In the unlikely event of a low altitude engine failure you are much more likely to hit in the in control level attitude then if you lose control in an attempted turn back.

The accident record is clear, turn backs are far more likely to end badly then just going straight ahead and incidentally hitting a house is very rarely fatal as the aircraft doesn't stop instantly, it has some small distance to decelerate which greatly reduces crash forces.

FWIW a steady 9 G deceleration from 60 to 0 takes about 25ft. At 9G there will be no injuries to anybody on the aircraft that is wearing a seat belt.

In the situation described I believe the safest course of action is to keep going straight and use any available power to help with the forced landing. If you were to decided to turn back I would suggest the safest course of action is to start a level medium banked turn back monitoring the airspeed. If at any time you can not maintain 1.3 Vs immediately roll wings level and land straight ahead.

[ahramin]

... start a level medium banked turn back monitoring the airspeed. If at any time you can not maintain 1.3 Vs immediately roll wings level and land straight ahead.

I think that right there is enough to survive most GA accidents.

[photofly]

incidentally hitting a house is very rarely fatal as the aircraft doesn't stop instantly, it has some small distance to decelerate which greatly reduces crash forces.

In this scenario, it’s not the people in the aircraft I’m concerned about. If you want to fly a piston single over a built up area, it’s not ok to risk the lives of people on the ground to save your own.

[torquey401]

http://www.nar-associates.com/technical ... screen.pdf

[PilotDAR]

I can't imagine ruddering a plane around at all, much less in an emergency, has any merit. If it were a good idea, it would be a) trained in flight training, and b) described in the emergency procedures section of flight manuals.

Cross controlling a plane adds drag, and decreases stability. If you're gliding in an emergency, those are two things you probably don't want - at least together!

[photofly]

Recall that a slip is also very much “crossed controls”, and slips in both straight and turning flight are taught and used in primary flight training, particularly during gliding descents when both slow, and low to the ground: think of practice (or real) forced landings, and regular landings in a plane with poor visibility over the nose or no flaps. In these scenarios the extra drag is welcomed.

The recovery from an aggravated stall involves entering an aggressive side slip, when applying rudder opposite to a dropping wing; this recovers stability, rather than hindering it. A slip is very much an “anti-spin”.

Let’s not get down on the concept of crossed controls just yet.

[digits_]

The recovery from an aggravated stall involves entering an aggressive side slip, when applying rudder opposite to a dropping wing; this recovers stability, rather than hindering it. A slip is very much an “anti-spin”.

But if you keep that input, you'll enter a spin in the opposite direction in a variety of airplanes... I wouldn't call it "anti-spin".

[photofly]

Depends on how much rudder you use and what you do with the ailerons. If you initially enter the slip, and then use the correct amount of rudder to maintain the slip along with ailerons, along with appropriate elevator then you will be stable. If you maintain full opposite rudder and neutral ailerons without recovering sufficient airspeed, so the aircraft skids the other way, then yes you’ll spin the other way.

It’s the slip that’s stable, not the spin recovery control inputs.

[Big Pistons Forever]

incidentally hitting a house is very rarely fatal as the aircraft doesn't stop instantly, it has some small distance to decelerate which greatly reduces crash forces.

In this scenario, it’s not the people in the aircraft I’m concerned about. If you want to fly a piston single over a built up area, it’s not ok to risk the lives of people on the ground to save your own.

I would suggest that the best way to avoid injuries to people on the ground is to maintain control of the aircraft. A botched turn back followed by a stall and spin, a very common result, is not helping anybody. I think that I also inadvertently implied that a glide straight ahead was perceived as not changing the aircraft heading 1 degree. What I meant by no straight ahead is the default is no turn back, however I would expect the pilot to maneuver while gliding ahead so as to avoid major obstacle if at all possible.

Again maintaining a safe speed and full control of the aircraft will IMO enable the highest likelihood of an accident with no fatalities and ideally minimal injures to people in the aircraft and on the ground. Of course the likelihood of success is greatly increased if a mental emergency brief which includes and awareness of the terrain options on the departure path. My admittedly completely personal opinion based on totally anecdotal observation on this is that most pilots do not do either before every takeoff.