High accident rates in light twins an alternative?
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>By the way, have another look at that chart that gave you 127kts cruise on one. TAS right? At what weight and what height? Work out what INDICATED speed that corresponds to, and get back to me!!<
Wizofox
I have over 2000 hrs on Seneca Fives/ From that start point 127 kts is IAS on the Five one out and level and at 2000 to 3000 feet.
Both running with a cruise setting of 29 man and 24rpm will indicate 155kts at 2000 to 3000 foot level.
I have flown these things at 20000 feet and the tas turns well over 200 kts with both engines running at 29 man 24rpm.
The five which is wastegated, turbocharged and intercooled performs far better than the earlier seneca 1, 2, 3, and 4 all of which I have also flown.
I also do not think we are miles apart and maybe the differences are more a misunderstanding of what we are both saying. I also appreciate your expertise but also my own in trying to extract the best I can from not only underpowered twins but light jets too.
Being a practical pilot maybe you can explain why a seneca at blue line of say 90 kts one out will only climb at grosse at 200 feet per minute but at level flight will accelerate to 127 kts? If it isnt to do with drag and especially drag from angle of attack.
I appreciate there are other forms of drag but the drag from angle of attack must outweigh the other drag for the aircraft to accelerate to 127 kts in level flight.
>If the BEST rate of climb is zero, flying any other speed produces a descent.<
Yes If the best rate of climb is zero and you have no extra power any reduction in AOA will result in an initial descent It has to!
But you are reducing drag by reducing AOA and you now have the bonus of tapping into Kinetic energy to add to the energy produced by your solitary engine.
From that initial descent the airspeed will increase as will the lift for that reduced AOA until you have level cruise, No descent and 127 kts IAS.
Pace
Wizofox
I have over 2000 hrs on Seneca Fives/ From that start point 127 kts is IAS on the Five one out and level and at 2000 to 3000 feet.
Both running with a cruise setting of 29 man and 24rpm will indicate 155kts at 2000 to 3000 foot level.
I have flown these things at 20000 feet and the tas turns well over 200 kts with both engines running at 29 man 24rpm.
The five which is wastegated, turbocharged and intercooled performs far better than the earlier seneca 1, 2, 3, and 4 all of which I have also flown.
I also do not think we are miles apart and maybe the differences are more a misunderstanding of what we are both saying. I also appreciate your expertise but also my own in trying to extract the best I can from not only underpowered twins but light jets too.
Being a practical pilot maybe you can explain why a seneca at blue line of say 90 kts one out will only climb at grosse at 200 feet per minute but at level flight will accelerate to 127 kts? If it isnt to do with drag and especially drag from angle of attack.
I appreciate there are other forms of drag but the drag from angle of attack must outweigh the other drag for the aircraft to accelerate to 127 kts in level flight.
>If the BEST rate of climb is zero, flying any other speed produces a descent.<
Yes If the best rate of climb is zero and you have no extra power any reduction in AOA will result in an initial descent It has to!
But you are reducing drag by reducing AOA and you now have the bonus of tapping into Kinetic energy to add to the energy produced by your solitary engine.
From that initial descent the airspeed will increase as will the lift for that reduced AOA until you have level cruise, No descent and 127 kts IAS.
Pace
Last edited by Pace; 30th May 2008 at 17:50.
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Pace,
Check out the following site:
http://selair.selkirk.bc.ca/aerodyna...lti/Page1.html
The top graph shows a graph of the power required to maintain level flight at a certain airspeed (the blue curve) and the power available (the red curve) at the same speed. When the red is above the blue, you have more power than you need and you can use that excess power to climb. And, if all you want to do is maintain level flight, you can do that at any speed between the two intersections of the lines. Hence, if you have a 200 fpm climb at 90 kts, it's possible that you may be able to accelerate out to 127.
Now look at the bottom graph. Specifically the lower red line. This illustrates the case where your power available is just equal to the power required to maintain level flight at one specific airspeed. That speed is Vyse. Now as you can see, if you try to accelerate away from Vyse, you end up making less power than what you need to keep level. This means you will descend until you return to Vyse. There's just no getting around it.
And finally, the "step climb" you keep talking about is actually called a zoom climb (yes, that really is the official technical term for it). It's a fighter jock move that you can use to temporarily get yourself to a point in space by trading kinetic energy for altitude. But as with anything in this world, it's not a perfect trade. You'll end up losing some of that energy to air resistance on the way up. It works on jets because they're travelling fast - lots of kinetic energy - and have extremely low drag - little air resistance. Compare that to light GA airplanes (especially a light twin with an engine out) where you have little energy and a lot of drag. At the speeds we're talking about here, the extra "smash" will buy you a few hundred fpm of climb for maybe 10 seconds, and then you're back to flying according to the curves above.
I also, from your comments about a "coffin corner," I think you're confusing Vyse with Vmca. If you slow below the blue line, it's not like going off a cliff. Just because the power required curve keeps going up doesn't mean that your airspeed will decrease uncontrollably. All it means is that you'll have to use "backside" techniques to fly the airplane - i.e. control airspeed with pitch and rate of climb with power. And since you're already asking for all the power you can, pitch is all you have left. So there's not even a training issue here. Now if you get below Vmca, that's a whole 'nother story.
Check out the following site:
http://selair.selkirk.bc.ca/aerodyna...lti/Page1.html
The top graph shows a graph of the power required to maintain level flight at a certain airspeed (the blue curve) and the power available (the red curve) at the same speed. When the red is above the blue, you have more power than you need and you can use that excess power to climb. And, if all you want to do is maintain level flight, you can do that at any speed between the two intersections of the lines. Hence, if you have a 200 fpm climb at 90 kts, it's possible that you may be able to accelerate out to 127.
Now look at the bottom graph. Specifically the lower red line. This illustrates the case where your power available is just equal to the power required to maintain level flight at one specific airspeed. That speed is Vyse. Now as you can see, if you try to accelerate away from Vyse, you end up making less power than what you need to keep level. This means you will descend until you return to Vyse. There's just no getting around it.
And finally, the "step climb" you keep talking about is actually called a zoom climb (yes, that really is the official technical term for it). It's a fighter jock move that you can use to temporarily get yourself to a point in space by trading kinetic energy for altitude. But as with anything in this world, it's not a perfect trade. You'll end up losing some of that energy to air resistance on the way up. It works on jets because they're travelling fast - lots of kinetic energy - and have extremely low drag - little air resistance. Compare that to light GA airplanes (especially a light twin with an engine out) where you have little energy and a lot of drag. At the speeds we're talking about here, the extra "smash" will buy you a few hundred fpm of climb for maybe 10 seconds, and then you're back to flying according to the curves above.
I also, from your comments about a "coffin corner," I think you're confusing Vyse with Vmca. If you slow below the blue line, it's not like going off a cliff. Just because the power required curve keeps going up doesn't mean that your airspeed will decrease uncontrollably. All it means is that you'll have to use "backside" techniques to fly the airplane - i.e. control airspeed with pitch and rate of climb with power. And since you're already asking for all the power you can, pitch is all you have left. So there's not even a training issue here. Now if you get below Vmca, that's a whole 'nother story.
But you are reducing drag by reducing AOA
Answer me these questions:-
Do you agree that a particular aircraft at a particular weight has ONE SPEED where it produces minimum TOTAL DRAG (that is, the sum of ALL types OF DRAG?) (and if you're not sure, have another look at the link I provided)
Do you agree that flying at ANY other speed increases drag?
Do you agree that said aircraft has ONE best rate of climb, single engine speed?
Do you agree that if the aircraft will only just maintain level at that speed, that it can't maintain level at any other speed?
The reason your aircraft will fly faster level than in climb is not because it produces less drag. Does your Seneca at 200kts produce less drag than when you are climbing it, two engine, at 150kts? If not, wouldn't it climb better at 200kts? But it doesn't, does it?
It flys faster because the excess thrust that was being used to produce the climb is now being used in level flight.
One misunderstanding you are demonstrating is the idea that you need more lift to climb. In unaccelerated flight, Lift=weight, and that goes for climb too. If lift is more than weight, you will accelerate vertically, that is "Pull G", and I'd think you would agree that a normal climb is a 1 G manoeuvre. Grab a PPL text book and have a look at the force vectors in level, climb and descent, and you'll see what I mean. A particular angle of attack produces a particular speed, whether climbing, level or descending.
What you advocate in the last sentence would work, PROVIDED you WERE able to climb at Vyse, even if only at a small rate. But if you can only maintain level at Vyse, by definition you will descend at any other speed.
And please don't bandy around kinetic energy. Aircraft fly because of the airflow over their wings and the speed and angle at which that happens. If you have more airflow, you can, in the short term, turn that into an increase in lift and a vertical acceleration, but that's aerodynamics, not grade school physics.
Next you'll be warning about down-wind turns and speed-loss due to momentum, but I KNOW you know better than that!!
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GR8handini
I agree with all you are saying here. Especially about what I referred to as step climbs and you referred to as zoom climbs.
Yes the faster you go in level flight the more kinetic energy you have to play with hence in light draggy aircraft you do not have a lot of margin.
In jets the margin between IAS and stall at high levels is much smaller so equally are the benefits of a zoom climb but it still can be played with in higher levels where your climb rate is poor but you still have enough margin to make a difference.
Go to high and you come down regardless or your in dead mans corner.
But it is still a game of playing with drag, power and kinetic energy.
I really dont think we are that far apart. All I will say about these Graphs is that they are designed for engine out CLIMBS and that is where we are apart because I am not referring to CLIMBS at all.
I do not fault or question these graphs or what they say.
Pace
I agree with all you are saying here. Especially about what I referred to as step climbs and you referred to as zoom climbs.
Yes the faster you go in level flight the more kinetic energy you have to play with hence in light draggy aircraft you do not have a lot of margin.
In jets the margin between IAS and stall at high levels is much smaller so equally are the benefits of a zoom climb but it still can be played with in higher levels where your climb rate is poor but you still have enough margin to make a difference.
Go to high and you come down regardless or your in dead mans corner.
But it is still a game of playing with drag, power and kinetic energy.
I really dont think we are that far apart. All I will say about these Graphs is that they are designed for engine out CLIMBS and that is where we are apart because I am not referring to CLIMBS at all.
I do not fault or question these graphs or what they say.
Pace
All I will say about these Graphs is that they are designed for engine out CLIMBS
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Wizofox
>No they're not. The drag/power curve is how much power you need to maintain LEVEL flight. If you have excess power over and above that, you can climb, or fly LEVEL at a faster speed. If you ONLY have enough power to fly level at the bottom of the curve, you CAN'T maintain level flight at any other speed.<
Where have I said that if you trying to climb at blue line on one engine have all the power available can you suddenly find more power to increase that speed.
You minimalise the importance of kinetic energy as part of your total energy management or somehow underate the ability to tap in and out of that.
I am sure you know of Bob Hoover. His party trick was to shut down both engines on his twin engined Shrike Commander dive the aircraft using totally kinetic energy find enough energy to pull the twin not only vertical but to do a complete loop and land off that loop engine out.
A glider the most basic form of aircraft with NO engines on a still calm day totally relies on kinetic energy for speed control and hence flight. I am sure you too have seen gliders towed to 3000 feet and released. I have seen aerobatic displays where the glider will run through a full range of aerobatics with no engine other than the Kinetic energy.
Your statement that reducing the angle of attack will have you going all the way down to the ground is far from the truth.
Speed does effect lift at a given angle of attack reduce that angle of attack and you reduce drag hence why in the seneca it will happily fly for hours at 127 kts level but will not do so with the same power at blue line. The reason for that is the aircraft is attempting to climb has no kinetic energy on tap and has a higher angle of attack than it would do at a faster speed in level flight.
These graphs are designed to show an incomplete picture and directed at single engine climb.
As you know the slower you go the more control inputs are required for a given effect, slow too much and you will have full rudder and not enough rudder to control the yaw and hence a stall, spin, scenario The same goes for all your other control surfaces.
Infact with the Seneca a slow speed pitching 7 degrees requires 8 inches of movement on the column try the same pitch at gently at cruise without breaking the plane and the column moves 2 cms.
Take the glider which has only one powerplant (kinetic energy) try and maintain level flight and the speed drops away. The AOA increases to maintain that altitude and continues to do so as speed bleeds off until the inevitable stall. Push the nose over and you tap back into kinetic energy and hey presto you are flying again.
It is this obsession with a climb and blue line which is the killer. The margins in that part of the envelope are so small especially where there is relatively so little power.
Trade some of that altitude (not a lot) for speed and and level flight and you are in a much more secure situation in some circumstances.
And no most of my flying nowadays is in business jets as a Captain but I still fly light twins and am not some sort of idiot like you like to make me out to be.
Pace
>No they're not. The drag/power curve is how much power you need to maintain LEVEL flight. If you have excess power over and above that, you can climb, or fly LEVEL at a faster speed. If you ONLY have enough power to fly level at the bottom of the curve, you CAN'T maintain level flight at any other speed.<
Where have I said that if you trying to climb at blue line on one engine have all the power available can you suddenly find more power to increase that speed.
You minimalise the importance of kinetic energy as part of your total energy management or somehow underate the ability to tap in and out of that.
I am sure you know of Bob Hoover. His party trick was to shut down both engines on his twin engined Shrike Commander dive the aircraft using totally kinetic energy find enough energy to pull the twin not only vertical but to do a complete loop and land off that loop engine out.
A glider the most basic form of aircraft with NO engines on a still calm day totally relies on kinetic energy for speed control and hence flight. I am sure you too have seen gliders towed to 3000 feet and released. I have seen aerobatic displays where the glider will run through a full range of aerobatics with no engine other than the Kinetic energy.
Your statement that reducing the angle of attack will have you going all the way down to the ground is far from the truth.
Speed does effect lift at a given angle of attack reduce that angle of attack and you reduce drag hence why in the seneca it will happily fly for hours at 127 kts level but will not do so with the same power at blue line. The reason for that is the aircraft is attempting to climb has no kinetic energy on tap and has a higher angle of attack than it would do at a faster speed in level flight.
These graphs are designed to show an incomplete picture and directed at single engine climb.
As you know the slower you go the more control inputs are required for a given effect, slow too much and you will have full rudder and not enough rudder to control the yaw and hence a stall, spin, scenario The same goes for all your other control surfaces.
Infact with the Seneca a slow speed pitching 7 degrees requires 8 inches of movement on the column try the same pitch at gently at cruise without breaking the plane and the column moves 2 cms.
Take the glider which has only one powerplant (kinetic energy) try and maintain level flight and the speed drops away. The AOA increases to maintain that altitude and continues to do so as speed bleeds off until the inevitable stall. Push the nose over and you tap back into kinetic energy and hey presto you are flying again.
It is this obsession with a climb and blue line which is the killer. The margins in that part of the envelope are so small especially where there is relatively so little power.
Trade some of that altitude (not a lot) for speed and and level flight and you are in a much more secure situation in some circumstances.
And no most of my flying nowadays is in business jets as a Captain but I still fly light twins and am not some sort of idiot like you like to make me out to be.
Pace
Pace,
Two quick questions which might help clear things up:-
1) At what speed do YOU believe your Seneca produces minimum TOTAL drag?
2) Why descend to accelerate? If you have excess power to climb at Vyse, simply leveling off will accelerate the aircraft with no height loss. If you DON'T, the aircraft will not maintain height at any other speed.
Two quick questions which might help clear things up:-
1) At what speed do YOU believe your Seneca produces minimum TOTAL drag?
2) Why descend to accelerate? If you have excess power to climb at Vyse, simply leveling off will accelerate the aircraft with no height loss. If you DON'T, the aircraft will not maintain height at any other speed.
I would get the old girl airborne let her accelerate to about Blue line +20 before putting the gear up and climbing away. I would be through 1000' AGL in no time. That way, if one quit prior to blueline +20
Do you factor in a flapless single engine landing after bunting over to force land straight ahead? Try touching down at Blue Line plus 15-20 knots and wheel barrow down the runway while trying to apply brakes with no anti-skid capability and that's ona dry hard surface let alone a wet runway. Try judging all this with a night forced landing on the remaining length of runway. This is just one of many examples of home-grown gimmicky "techniques" that plague the general aviation pilot population.
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>Why descend to accelerate? If you have excess power to climb at Vyse, simply leveling off will accelerate the aircraft with no height loss. If you DON'T, the aircraft will not maintain height at any other speed.<
We are talking about a situation which can and does occur with a light twin when at grosse weight, an old aircraft with tired engines rather than the immaculate test machine the manufacturers use to get their paltry 200 fpm at grosse on a standard day doesnt climb.
I was just in that situation a few years ago loosing an engine at 200 feet at grosse on an above temp day. Luckily for me I decided to go against my "trained" procedures. I decided to keep the damaged engine going as although the vibrations were bad it was still producing maybe 30% pwr.
I knew without any shadow of a doubt that if I shut down I was going down NO question.
I placed one hand on the prop lever ready to pull it had it gone bang and yes flew blue line until 1000 feet at approx 150 feet per min. Had I shut the damaged engine down I can assure you that the aircraft would have gone nowhere but down into the trees blue line minumum drag or whatever. So lucky I used my brains rather than slavishly following procedures.
Once in level cruise I shut the engine down and Majic 125+ kts and a relatively simple piece of cake. Cause was three sheared rocker shafts.
Explain that situation to me ? Why was the plane a dog at blue line and I pride myself at my technique and a doddle at 125+ kts and level. Once at 125+kts the aircraft lost NO altitude and that is a fact with light twins. They do not climb well if at all on one but cruise happily at a reduced power setting on one in level cruise.
All I have said from the start of this thread this is a techique given to me by a fighter pilot and because of my real world experience I gave it a thorough trying out. Of COURSE if you are getting a healthy climb at blue line continue.
But if you are not loose a little height tap into kinetic energy and establish a level cruise. If that fails go for the trees anyway as you havent lost a thing.
Pace
We are talking about a situation which can and does occur with a light twin when at grosse weight, an old aircraft with tired engines rather than the immaculate test machine the manufacturers use to get their paltry 200 fpm at grosse on a standard day doesnt climb.
I was just in that situation a few years ago loosing an engine at 200 feet at grosse on an above temp day. Luckily for me I decided to go against my "trained" procedures. I decided to keep the damaged engine going as although the vibrations were bad it was still producing maybe 30% pwr.
I knew without any shadow of a doubt that if I shut down I was going down NO question.
I placed one hand on the prop lever ready to pull it had it gone bang and yes flew blue line until 1000 feet at approx 150 feet per min. Had I shut the damaged engine down I can assure you that the aircraft would have gone nowhere but down into the trees blue line minumum drag or whatever. So lucky I used my brains rather than slavishly following procedures.
Once in level cruise I shut the engine down and Majic 125+ kts and a relatively simple piece of cake. Cause was three sheared rocker shafts.
Explain that situation to me ? Why was the plane a dog at blue line and I pride myself at my technique and a doddle at 125+ kts and level. Once at 125+kts the aircraft lost NO altitude and that is a fact with light twins. They do not climb well if at all on one but cruise happily at a reduced power setting on one in level cruise.
All I have said from the start of this thread this is a techique given to me by a fighter pilot and because of my real world experience I gave it a thorough trying out. Of COURSE if you are getting a healthy climb at blue line continue.
But if you are not loose a little height tap into kinetic energy and establish a level cruise. If that fails go for the trees anyway as you havent lost a thing.
Pace
Pace,
In my last few posts I have asked you a series of questions intended to clarify your knowledge of this subjest. You haven't answered one, but have rather given touching monolouges of a "There I was" type.
If you want to compare CVS, go ahead, I'll win.
If you want to have a disscustion about aerodynamics, answer my questions (the last two will do!) and we can go on. If not, I'm not interested.
As to your question, it was a doddle at 125kts because all the available power was being used to maintain level flight. There was, therefore, excess power over and above minimum drag. At Vyse you WOULD have had a positive climb, however small.If that was not the case, the aircraft
could not maintain level flight whilst at other the Best rate, now could it?
Did it occur to you that your broken engine may have produced drag through a basically windmilling prop rather that thrust?
In my last few posts I have asked you a series of questions intended to clarify your knowledge of this subjest. You haven't answered one, but have rather given touching monolouges of a "There I was" type.
If you want to compare CVS, go ahead, I'll win.
If you want to have a disscustion about aerodynamics, answer my questions (the last two will do!) and we can go on. If not, I'm not interested.
As to your question, it was a doddle at 125kts because all the available power was being used to maintain level flight. There was, therefore, excess power over and above minimum drag. At Vyse you WOULD have had a positive climb, however small.If that was not the case, the aircraft
could not maintain level flight whilst at other the Best rate, now could it?
Did it occur to you that your broken engine may have produced drag through a basically windmilling prop rather that thrust?
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Wasting your time, Wiz, pace has his mind made up, as in....don't confuse me with the facts, my mind is made up.
Best ignored.
As are a very few others on this forum who exhibit juvenile...ah, tendancies.
Best ignored.
As are a very few others on this forum who exhibit juvenile...ah, tendancies.
Yeah, don't listen to 411A---very inexperienced
--he has only circled low a few times in 720B ----easy
and his name--what would he know about the ASI blue line?--best put him on ignore list ---so that you can go crash into a mountain
PA
--he has only circled low a few times in 720B ----easyand his name--what would he know about the ASI blue line?--best put him on ignore list ---so that you can go crash into a mountain
PA
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BRING BACK THE MAYTAG
Thanks Guys!
Yes, the forhead has been getting a workout on the wall here!!
But I think Pace is an alright guy, unlike that idiot Angels 60.
What he is actuall saying isn't too far from right, he just doesn't quite realise that what he is sugesting as a technique doesn't match up with the pseudo aerodynamics he quotes.
He keeps on banging on about "Reducing AS of A reduces drag", and the clue was he heard it from a fighter pilot. He's talking about UNLOADING i.e bunting over and flying at less than 1 G. Well, that will sure make you accelerate- in a light twin on 1 at 200' it will accelerate you for the whole 3 seconds to the ground!! When I tried to explain that, at 1 G, min drag is as good as it gets, things got a bit cloudy. Similarly, telling him that if you can't climb at Vyse, you can't maintain height at any other speed didn't sit well because he's convinced you REDUCE drag by accelerating to a faster speed.
As to what he's actually saying, accelerate or even descend to a substainial margin above Vyse, might have merit in some circumstances, though I know I would probably want to at least hold onto the height I had!!
Yes, the forhead has been getting a workout on the wall here!!
But I think Pace is an alright guy, unlike that idiot Angels 60.
What he is actuall saying isn't too far from right, he just doesn't quite realise that what he is sugesting as a technique doesn't match up with the pseudo aerodynamics he quotes.
He keeps on banging on about "Reducing AS of A reduces drag", and the clue was he heard it from a fighter pilot. He's talking about UNLOADING i.e bunting over and flying at less than 1 G. Well, that will sure make you accelerate- in a light twin on 1 at 200' it will accelerate you for the whole 3 seconds to the ground!! When I tried to explain that, at 1 G, min drag is as good as it gets, things got a bit cloudy. Similarly, telling him that if you can't climb at Vyse, you can't maintain height at any other speed didn't sit well because he's convinced you REDUCE drag by accelerating to a faster speed.
As to what he's actually saying, accelerate or even descend to a substainial margin above Vyse, might have merit in some circumstances, though I know I would probably want to at least hold onto the height I had!!
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Wiz
I think you nailed it. Pace wants to trade energy for AS but not pay up after the bargain is struck. Energy lost is time on the Planet in dire straits. No Piston Twin I am aware of is anything but borrowed time on 1. My God I hate the Horn. ETOPS they ain't. The Polar has a temptress, and if one isn't careful, it can seem that the slower one flies, the more Lift one has at their disposal. Following that logic, Maximum Lift is derived while waiting to Taxi out. No Free Lunch? Come to think of it, maybe I'm thinking of Angels60 and his urge to rotate prior to Vmc. Which I think is what's called an oxymoron. Or was it Rotate prior to Vmc and reject at V1+1? Or is Pace suggesting a "zoom" descent?
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Lots of talk about the "engine" being kinetic energy.
If you have lost an engine on a hot day at MTOW at say 400 feet plus, and if there is a nice field waiting for you just ahead, why not use the other engine:
Potential Energy to make a stress less landing and its home for tea and biscuits!
I'm going to be doing some twin flying soon and therefore not an expert...but my mentality will be chop and controlled landing given the field I fly from and the average density altitude experienced there.
Best,
Sicknote
If you have lost an engine on a hot day at MTOW at say 400 feet plus, and if there is a nice field waiting for you just ahead, why not use the other engine:
Potential Energy to make a stress less landing and its home for tea and biscuits!
I'm going to be doing some twin flying soon and therefore not an expert...but my mentality will be chop and controlled landing given the field I fly from and the average density altitude experienced there.
Best,
Sicknote
It's been a long time since my piston twin days but I think Pace has a point or two here.
We're not dealing with perf-A aircraft, so there is no magical flight path to attain which will assure safe continued OEI flight up to MSA. I would agree that concentrating all your efforts on keeping blue-line when you could add a reasonable buffer and still climb or maintain altitude seems like a sensible idea to me. Dropping much below Vyse (for whatever reason) towards Vmca has such serious consequences that the above seems like a reasonable trade.
I don't have any graphs in front of me but if you can - and I'm going off the figures presented here - (just) climb a light twin at 90kts OEI but also cruise it level at 127kts at the same mass, then you'd have thought there was a continuous range of speeds between these two where you could trade ROC for airspeed. If this is not the case, then there must be some rather peculiar drag characteristics, maybe requiring special techniques to generate a transient drag reduction/effective power increase (gentle pushover & descent) to allow acceleration into a more favourable regime and a resumption of level flight or climb.
IMHO, it's not flying level or even slowly descending that's dangerous; there is time to correct this and after all, you have to descend at some point to land! It is the potential loss of control from asymmetry that's the killer and airspeed is most definitely your friend here. You don't need to be in a light twin, either - an empty A330 with a very high power-to-weight ratio will do exactly the same thing, as demonstrated at Toulouse in 1994...
We're not dealing with perf-A aircraft, so there is no magical flight path to attain which will assure safe continued OEI flight up to MSA. I would agree that concentrating all your efforts on keeping blue-line when you could add a reasonable buffer and still climb or maintain altitude seems like a sensible idea to me. Dropping much below Vyse (for whatever reason) towards Vmca has such serious consequences that the above seems like a reasonable trade.
I don't have any graphs in front of me but if you can - and I'm going off the figures presented here - (just) climb a light twin at 90kts OEI but also cruise it level at 127kts at the same mass, then you'd have thought there was a continuous range of speeds between these two where you could trade ROC for airspeed. If this is not the case, then there must be some rather peculiar drag characteristics, maybe requiring special techniques to generate a transient drag reduction/effective power increase (gentle pushover & descent) to allow acceleration into a more favourable regime and a resumption of level flight or climb.
IMHO, it's not flying level or even slowly descending that's dangerous; there is time to correct this and after all, you have to descend at some point to land! It is the potential loss of control from asymmetry that's the killer and airspeed is most definitely your friend here. You don't need to be in a light twin, either - an empty A330 with a very high power-to-weight ratio will do exactly the same thing, as demonstrated at Toulouse in 1994...
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Missing link?
I can take the ribbing but am trying to have a serious discussion. To clear up a few points yes it is obvious that the faster you go the more drag there will be, not in question. Take an aircraft on the ground no speed no drag any speed above no speed will create drag.
VYSE is the speed set in the climb where on one engine you have minumum drag and the best speed to make the maximum climb possible.
I have gone on a lot about KINETIC energy, talked about the power of that energy talked about Bob Hoover looping his twin using nothing but Kinetic energy.Talked about gliders. I have talked about total energy management which is not just from an engine.
I am sure Wizofox in his 777 knows only too well that if he leaves cruise thrust set and descends his aircraft will accelerate due to Kinetic energy plus his thrust. If he does nothing his 777 will accelerate through VNE.
I am shown graphs designed at a single engine climb and power from an engine and these are used to rubbish cruise. Fair enough but then that in itself is a blinkered misconception.
I have asked Wizofox to explain scientifically an undisputable fact as I appreciate his expertise. What am I but a practical pilot not a scientist.
That undesputable fact in simple terms is that the majority of twins will cruise happily on one engine in level flight but are pigs in producing any sort of climb. Infact some light twins dont claim to climb at all engine out (I am thinking of that old twin engined bi-plane forgot the name ) but it will cruise level on one.
Wizofox fails to respond with the scientific/ aerodynamic reasononing for the above and gets out of it by demanding I answer irrelevent questions to the arguement of his first.
My guess not being a scientist is that in any climb situation there is only one energy source available and that is the remaining engine. That remaining engine has NO assistance from Kinetic energy as the aircraft and engine are in a negative situation. The remaining engine trying to drag the aircraft skywards and in the process making the most of the process by selecting a minimum drag profile and speed.
Once in level cruise the aircraft is not in a negative situation. Yes because it is going faster there is more drag. Any speed above the speed needed to maintain altitude in the cruise is a bonus and now becomes a mixture of engine power and Kinetic energy. Because the engine is no longer trying to drag the airframe skywards there is excess power to maintain level speed only and the aircraft accelerates.
So Wizofox with all your knowledge please enlighten me to the relevant scientific facts of why a twin will fly happily for hours on one But will not climb? Then we might get somewhere.
Pace
VYSE is the speed set in the climb where on one engine you have minumum drag and the best speed to make the maximum climb possible.
I have gone on a lot about KINETIC energy, talked about the power of that energy talked about Bob Hoover looping his twin using nothing but Kinetic energy.Talked about gliders. I have talked about total energy management which is not just from an engine.
I am sure Wizofox in his 777 knows only too well that if he leaves cruise thrust set and descends his aircraft will accelerate due to Kinetic energy plus his thrust. If he does nothing his 777 will accelerate through VNE.
I am shown graphs designed at a single engine climb and power from an engine and these are used to rubbish cruise. Fair enough but then that in itself is a blinkered misconception.
I have asked Wizofox to explain scientifically an undisputable fact as I appreciate his expertise. What am I but a practical pilot not a scientist.
That undesputable fact in simple terms is that the majority of twins will cruise happily on one engine in level flight but are pigs in producing any sort of climb. Infact some light twins dont claim to climb at all engine out (I am thinking of that old twin engined bi-plane forgot the name ) but it will cruise level on one.
Wizofox fails to respond with the scientific/ aerodynamic reasononing for the above and gets out of it by demanding I answer irrelevent questions to the arguement of his first.
My guess not being a scientist is that in any climb situation there is only one energy source available and that is the remaining engine. That remaining engine has NO assistance from Kinetic energy as the aircraft and engine are in a negative situation. The remaining engine trying to drag the aircraft skywards and in the process making the most of the process by selecting a minimum drag profile and speed.
Once in level cruise the aircraft is not in a negative situation. Yes because it is going faster there is more drag. Any speed above the speed needed to maintain altitude in the cruise is a bonus and now becomes a mixture of engine power and Kinetic energy. Because the engine is no longer trying to drag the airframe skywards there is excess power to maintain level speed only and the aircraft accelerates.
So Wizofox with all your knowledge please enlighten me to the relevant scientific facts of why a twin will fly happily for hours on one But will not climb? Then we might get somewhere.
Pace
Last edited by Pace; 1st Jun 2008 at 15:29.
Because the power required for a climb is not equal to the power available---
aircraft performance summarized in two words---power required, power available---very difficult concept
no se lode a nadie
PA
aircraft performance summarized in two words---power required, power available---very difficult concept
no se lode a nadie
PA
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>Because the power required for a climb is not equal to the power available<
Pugilistic animus
Thank you in a few words you say it all. Hence why attempting to climb an unclimbing aircraft is a waste of time but going for a single engine cruise is not. Finally some sense
Pace
Pugilistic animus
Thank you in a few words you say it all. Hence why attempting to climb an unclimbing aircraft is a waste of time but going for a single engine cruise is not. Finally some sense
Pace