Top rudder in turns
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As for the original thread some aircraft do tend to display a tendancy for just a touch of top rudder during sustained turns. In principal they shoudn't but they do. At the end of the day if the ball is centered during a sustained turn then it is safe to say you a pretty well in a balanced turn.
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Ok, Stupid-trainee question time
define "top rudder"
is is this full travel of rudder peddles / auctuators? or something else.
just makeing sure i am reading the thread correctly
define "top rudder"
is is this full travel of rudder peddles / auctuators? or something else.
just makeing sure i am reading the thread correctly
"Top rudder" is when you apply rudder towards the outside of a turn. So in a right turn you'd apply left rudder (called top rudder becaue you are pushing with the leg that is at the "top" of the aircraft.) The instructor in the OP suggests applying top rudder in a steep turn to keep the nose up. This is a load of crap in my opinion. Top rudder will put you out of balance which increases drag which degrades performance which is the last thing you want in a steep turn.
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Top rudder
Um. For what it's worth, one of the aircraft I fly - a Spezio Tuholer, which is an old design taildragger - definitely seems to require some top rudder in steep turns to keep it in balance. I don't know why, but it does. Over a certain bank angle, if I don't use top rudder, it ?slips TOWARDS the turn. I recall one of my instructors, a long time ago, telling me something like "quite a few old biplanes require a little top rudder in turns". Could be a myth, I guess, although it certainly seems real enough when I fly the Spezio. It's a draggy monoplane, not a biplane, with a lot of adverse yaw, yaw/roll coupling, and so on. I've never needed top rudder in a Cessna though...
...and in another aircraft, a Harmon Rocket, I REALLY struggle to get the damn thing down without risking shock cooling, cos it's so overpowered & fast. It's a little tricky cos my airstrip (1500 ft ASL) is right after a mountain pass of about 5500 ft. After a great deal of experimentation, I've settled on this procedure:
Gradually cool the engine for a few minutes on approach if possible, over the last mountain pass at about 6000 feet, then a high speed cruise descent, if turbulence permits, to 3500 or so - then cut power very briefly, one or two tight 360s, (without using much control deflection so as not to blow VA), to slow down and put full flap down at 115 knots, and then power up again, at 100 knots, and slip or spiral the rest of the way down. I'm not all that happy with it - would prefer not to cut the engine at all - but it seems to be the only way to get down fast without putting excess stress on the airframe, or risking shock cooling the engine. (And I have to get it down fast because of noise abatement issues - otherwise of course I could just fly around in a more sedate manner. Unfortunately this is not a good option, politically speaking, although clearly the best otherwise.)
I would be very interested to know if anyone has any better suggestions for descending quickly in a slippery, very powerful piston engined aircraft. Normal cruise is about 200 knots, VFE is 120. It's fast enough that it'll set off the shock cooling alarm in level flight, at full power, immediately after takeoff, so I usually have to keep her climbing, just to slow down the rate of cooling of the engine. Or not take off at full power, which is of course not recommended. After a normal flight, prior to descent, CHTs can be up to 360, and I note that my shock cooling alarms switches off at 300. Does this mean that at CHTs below 300, shock cooling is not an issue?
Seems to me that a bootful of rudder at 130 knots would definitely risk blowing VA, in many aircraft, but no doubt Sir Pratt knows his machine...
...and in another aircraft, a Harmon Rocket, I REALLY struggle to get the damn thing down without risking shock cooling, cos it's so overpowered & fast. It's a little tricky cos my airstrip (1500 ft ASL) is right after a mountain pass of about 5500 ft. After a great deal of experimentation, I've settled on this procedure:
Gradually cool the engine for a few minutes on approach if possible, over the last mountain pass at about 6000 feet, then a high speed cruise descent, if turbulence permits, to 3500 or so - then cut power very briefly, one or two tight 360s, (without using much control deflection so as not to blow VA), to slow down and put full flap down at 115 knots, and then power up again, at 100 knots, and slip or spiral the rest of the way down. I'm not all that happy with it - would prefer not to cut the engine at all - but it seems to be the only way to get down fast without putting excess stress on the airframe, or risking shock cooling the engine. (And I have to get it down fast because of noise abatement issues - otherwise of course I could just fly around in a more sedate manner. Unfortunately this is not a good option, politically speaking, although clearly the best otherwise.)
I would be very interested to know if anyone has any better suggestions for descending quickly in a slippery, very powerful piston engined aircraft. Normal cruise is about 200 knots, VFE is 120. It's fast enough that it'll set off the shock cooling alarm in level flight, at full power, immediately after takeoff, so I usually have to keep her climbing, just to slow down the rate of cooling of the engine. Or not take off at full power, which is of course not recommended. After a normal flight, prior to descent, CHTs can be up to 360, and I note that my shock cooling alarms switches off at 300. Does this mean that at CHTs below 300, shock cooling is not an issue?
Seems to me that a bootful of rudder at 130 knots would definitely risk blowing VA, in many aircraft, but no doubt Sir Pratt knows his machine...
Last edited by lostpianoplayer; 25th Dec 2006 at 10:20. Reason: still ambiguous
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Im not too sure what to say to the "top of rudder" in a turn, maybe you were out of balance?
As for high speed decents
21/21 and 140kts or just below WX pending (top of green arc) worked well for me in a C182, got me 2000fpm average on the way down, sometimes 2500fpm average if the weather was ncie to me. All of this was done with WINGS LEVEL AND IN BALANCE! 
Normal practise for me was to go 7nm out and then come back in and that will give me a nice profile for CCT entry and landing, or if I was giving a distance limitation then (3-5nm) then the RoD will decrease in a turn, thus taking a bit longer to go down!
Give me a turbine anyday for PJE mmmm beta.... have they got an STC out for a "gate" like fitting so when all the jumpers get out you can shut this gate and it blocks off the Relative airflow through the engine cowling? that would make idle decents in pistons achievable, and faster turn around times!
Merry Xmas to all
CMN
As for high speed decents
21/21 and 140kts or just below WX pending (top of green arc) worked well for me in a C182, got me 2000fpm average on the way down, sometimes 2500fpm average if the weather was ncie to me. All of this was done with WINGS LEVEL AND IN BALANCE! Normal practise for me was to go 7nm out and then come back in and that will give me a nice profile for CCT entry and landing, or if I was giving a distance limitation then (3-5nm) then the RoD will decrease in a turn, thus taking a bit longer to go down!
Give me a turbine anyday for PJE
mmmm beta.... have they got an STC out for a "gate" like fitting so when all the jumpers get out you can shut this gate and it blocks off the Relative airflow through the engine cowling? that would make idle decents in pistons achievable, and faster turn around times!Merry Xmas to all
CMN
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Thanks Aerocat, i was wondering why it didn't seem to make sense ...
to correct for a bad habit of over-defecting rudder into turn maybe? ....even that explination doesn't feel right, although i can't express why. maybe i am forgetting the physics involved
to correct for a bad habit of over-defecting rudder into turn maybe? ....even that explination doesn't feel right, although i can't express why. maybe i am forgetting the physics involved
Grandpa Aerotart
lostpianoplayer et al.
Shock cooling is more myth than fact.
What engine/prop are you running in your Harmon Rocket?
In my Bonanza (IO550b/3 bladed Blac Mac) I can prove it to you with the EDM 700 engine monitor. I generally cruise LOP but the same theory works ROP. I have shown a very experienced CFI and he just shook his head in disbelief...before walking away, and I strongly suspect, convincing himself he didn't really see what he thought he saw.
What I do on descent is the following.
When I want to descend I poke the nose down for a desired rate of descent.
As speed builds up I wind back the rpm...eventually all the way back to min governing.
When that is not enough to keep the speed in the green (about 3000') I reach out and in one smooth motion pull the throttle back from wide open, where it has been since takeoff, to around 16in MP. In doing so I dramatically decrease the air available to the combustion chambers and this enrichens the mixture from about 30-40F LOP to 50F ROP. 50-80F ROP is the hottest place to run your engine from a CHT point of view.
When I do that all the EGT bar graphs in the engine monitor increase (richer mixture burns hotter when you start from LOP) and the rate at which the CHTs cool actually slows down...this is the bit the CFI couldn't get his head around...the CHTs cool slower but I am still on a high speed descent with the IAS at the top of the green arc but the throttle pulled out to just above gear warning horn. You can actually see them ticking down a degree at a time on descent and when I pull the throttle they almost stop ticking down...the rate of cooling visibly slows.
I would be prepared to bet folding money the alarm sounding in this case is not your shock cooling alarm. It is more likely to be a high CHT alarm which may be set too low...what is that set at now? If it is set at less than 400F it is set too low. If your hottest cylinders see 360F just after takeoff that is no problem at all. Keep them at less than 380F in cruise...if you're running an injected Continental without GAMIjectors I strongly recommend fitting them.
On descent do as I do and if you're running ROP just lean the mixture enough to be around peak EGT. In this configuration, peak EGT and min RPM you can happily pull the throttle back with no fear of shock cooling anything because you will be effectively enrichening the mixture to around 50-80F ROP when you reduce throttle. You may find they are around 300-330F when you pull the throttle closed...they can't shock cool at this point because they are already cool.
As you approach circuit ht pull the throttle back to 12-13in MP and carry that into the circuit. You will find even if you hit the circuit at 200kts, one 180 degree turn...upwind to downwind...say 45 degree AOB level turn with a little 'G' will have you down to flap speed without all the carryon you're experiencing now...and with really low RPM and low MP you will be effectively in stealth mode and the neighbours likely won't hear you at all.
With a little practice and thought you will be able to time it so you hit flap speed abeam the landing threshold and simply add flap in a constant turn onto final while leaving the power alone...once down to approach speed on final the prop will be on the fine pitch stop anyway and you can shove it up to full fine for a go around without it making any noise at all.
Top rudder in a steep turn?
Not unless you're flying something with massive torque, like a Spitfire, Mustang, Bearcat etc...or something with very strange aerodynamics. Neither case applicable here I think.
Shock cooling is more myth than fact.
What engine/prop are you running in your Harmon Rocket?
In my Bonanza (IO550b/3 bladed Blac Mac) I can prove it to you with the EDM 700 engine monitor. I generally cruise LOP but the same theory works ROP. I have shown a very experienced CFI and he just shook his head in disbelief...before walking away, and I strongly suspect, convincing himself he didn't really see what he thought he saw.
What I do on descent is the following.
When I want to descend I poke the nose down for a desired rate of descent.
As speed builds up I wind back the rpm...eventually all the way back to min governing.
When that is not enough to keep the speed in the green (about 3000') I reach out and in one smooth motion pull the throttle back from wide open, where it has been since takeoff, to around 16in MP. In doing so I dramatically decrease the air available to the combustion chambers and this enrichens the mixture from about 30-40F LOP to 50F ROP. 50-80F ROP is the hottest place to run your engine from a CHT point of view.
When I do that all the EGT bar graphs in the engine monitor increase (richer mixture burns hotter when you start from LOP) and the rate at which the CHTs cool actually slows down...this is the bit the CFI couldn't get his head around...the CHTs cool slower but I am still on a high speed descent with the IAS at the top of the green arc but the throttle pulled out to just above gear warning horn. You can actually see them ticking down a degree at a time on descent and when I pull the throttle they almost stop ticking down...the rate of cooling visibly slows.
It's fast enough that it'll set off the shock cooling alarm in level flight, at full power, immediately after takeoff
On descent do as I do and if you're running ROP just lean the mixture enough to be around peak EGT. In this configuration, peak EGT and min RPM you can happily pull the throttle back with no fear of shock cooling anything because you will be effectively enrichening the mixture to around 50-80F ROP when you reduce throttle. You may find they are around 300-330F when you pull the throttle closed...they can't shock cool at this point because they are already cool.
As you approach circuit ht pull the throttle back to 12-13in MP and carry that into the circuit. You will find even if you hit the circuit at 200kts, one 180 degree turn...upwind to downwind...say 45 degree AOB level turn with a little 'G' will have you down to flap speed without all the carryon you're experiencing now...and with really low RPM and low MP you will be effectively in stealth mode and the neighbours likely won't hear you at all.
With a little practice and thought you will be able to time it so you hit flap speed abeam the landing threshold and simply add flap in a constant turn onto final while leaving the power alone...once down to approach speed on final the prop will be on the fine pitch stop anyway and you can shove it up to full fine for a go around without it making any noise at all.
Top rudder in a steep turn?
Not unless you're flying something with massive torque, like a Spitfire, Mustang, Bearcat etc...or something with very strange aerodynamics. Neither case applicable here I think.
Last edited by Chimbu chuckles; 26th Dec 2006 at 15:52.
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Use the balance ball
Top rudder is a useful descriptive phrase. While performing a turn, Aileron controls bank angle, elevator controls attitude (and therefore altitude), and rudder controls balance.
If the student concerned has put too much bottom rudder on (blindly believing that left turn always needs left rudder and right turn always needs right rudder) then a touch of top rudder will put the balance ball in the middle.
If you read the POH for Cessna 152 Aerobat, there is an aerobatic manouver that starts with a max-rate turn. When you apply full top rudder and full back elevator, the aircraft will flick over into a max-rate turn the other way (if you catch it at the right time). Good handling exercise - as well as a demonstration of why flying out of balance on a turn is not recommended - meat bombers take note.
Have fun.
ECT?
If the student concerned has put too much bottom rudder on (blindly believing that left turn always needs left rudder and right turn always needs right rudder) then a touch of top rudder will put the balance ball in the middle.
If you read the POH for Cessna 152 Aerobat, there is an aerobatic manouver that starts with a max-rate turn. When you apply full top rudder and full back elevator, the aircraft will flick over into a max-rate turn the other way (if you catch it at the right time). Good handling exercise - as well as a demonstration of why flying out of balance on a turn is not recommended - meat bombers take note.
Have fun.
ECT?
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From memory (its been awhile since i've flown a 206) 10' flap speed is about 140kts? (top of the green) Thats been in every 206 i've flown anyway. so 22'' 2200 rpm and away you go. You should get at least 2000 fpm if not more.
If you ever get a chance to use a digital cht gauge you'll actually see the major cooling takes place in the first two minutes of decent after that the temp stays pretty much the same no matter what you do.
octa
If you ever get a chance to use a digital cht gauge you'll actually see the major cooling takes place in the first two minutes of decent after that the temp stays pretty much the same no matter what you do.
octa
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i've tried that flick manouvre - i found it difficult to master tidily. looks easy in the poh though. the pitts does it with ease
and although thermal shock is not distinct/limited to the conti 520 found in most 206s, it is a significant consideration as they are suspectible to cracking. the 540 lycoming is not as 'fragile', but chuck a turbo on it (ala chieftan) and try to convince an owner to let you do assymetrical flight in it.
and the 550's have a less than desireable history when used for parachute ops.
a pt6 would solve most the problems....
but anyway, this is about top rudder.......
and although thermal shock is not distinct/limited to the conti 520 found in most 206s, it is a significant consideration as they are suspectible to cracking. the 540 lycoming is not as 'fragile', but chuck a turbo on it (ala chieftan) and try to convince an owner to let you do assymetrical flight in it.
and the 550's have a less than desireable history when used for parachute ops.
a pt6 would solve most the problems....
but anyway, this is about top rudder.......
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From memory (its been awhile since i've flown a 206) 10' flap speed is about 140kts? (top of the green) Thats been in every 206 i've flown anyway. so 22'' 2200 rpm and away you go. You should get at least 2000 fpm if not more.
If you ever get a chance to use a digital cht gauge you'll actually see the major cooling takes place in the first two minutes of decent after that the temp stays pretty much the same no matter what you do.
octa
If you ever get a chance to use a digital cht gauge you'll actually see the major cooling takes place in the first two minutes of decent after that the temp stays pretty much the same no matter what you do.
octa
the white arc is flap range.
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use those FEET
one has to remember, rudder is sort of the forgotton flight control, i know of pilots who think its only for steering on the ground and kicking it straight before touchdown!
I am lucky to have a boss who is a rudder fanatic and he makes sure everyone knows what they are for.
I've been lucky enough to fly the Tucano (1200hp tandem seat trainer) and that bad boy uses some serious rudder! Only time I have used top rudder though is during a slow roll or 4 point turn, and that feels damned awkward so JUST KEEP IT IN BALANCE!
Grandpa Aerotart
I use 'top' rudder in a turn everytime I fly my Bonanza...turning left onto crosswind after takeoff with full power (lots of torque) and slow speed...less than 110kts usually....If I was turning right I would be using more right or 'bottom' rudder...and actually when I use 'top'/right rudder on the left turn I am actually using less right rudder than was the case before the turn commenced...if you get my drift
Like I said above...lots of torque or strange aerodynamics...and I would be very surprised if many/any aeroplanes have flown/still fly with aerodynamic properties that strange...plenty with lots of torque/P factor at slow speed though.
AP I assume you mean 4 point roll not 4 point turn
Like I said above...lots of torque or strange aerodynamics...and I would be very surprised if many/any aeroplanes have flown/still fly with aerodynamic properties that strange...plenty with lots of torque/P factor at slow speed though.
AP I assume you mean 4 point roll not 4 point turn
I use 'top' rudder in a turn everytime I fly my Bonanza...turning left onto crosswind after takeoff with full power (lots of torque) and slow speed...less than 110kts usually....If I was turning right I would be using more right or 'bottom' rudder...and actually when I use 'top'/right rudder on the left turn I am actually using less right rudder than was the case before the turn commenced...if you get my drift
If, in the OPs case, he was guilty of flying out of balance and the instructor was telling him to use some top rudder for that reason alone, then that is poor instructional technique and confusing.