High accident rates in light twins an alternative?

[Pace]

We all know that the accident rate for light twins is attrocious with an engine failure.

Infact I believe you are more likely to survive a single engine failure and the subsequent forced landing than an engine failure in a twin.

Most light twins at best at grosse weight on a standard day are hard pushed to climb at 200 fpm and those figures are achieved on new aircraft with new engines, not old hanger rash aircraft, covered in flies with tired old engines.

With the second engine comes more options and with more options comes more opportunities for making a mistake.

I appreciate the high accident rate is partially due to the fact that most private pilots cannot afford to fly light twins and as such are not current enough to cope.

But where does the training figure in this high level of accidents.
We are taught to act in a particular way to an engine failure and have it drummed into us to such an extent that we go into mental autopilot and with the aircraft cleaned up go for blue line and a climb.

I have had three engine failures in my time. Two partial one full. One was at grosse and at 200 feet in the climbout. The aircraft was shaking badly but the engine was still producing some power. I elected to keep it going as even with some power I realised that I was not going to climb at all if I shut it down. I had one hand on the prop lever ready to pull it if there was a bang and then once up at a 1000 feet shut the engine down. The cause was three Sheared rocker shafts.

Another alternative was put to me by an ex fighter pilot for light twins and may be an option to add in certain circumstances.

While light twins are happy to fly along in level cruise with one shut down all day they are pathetic at best at blue line climbing. You only need a gusty day with downdrafts a desperation and fix on climbing and it is only too easy to get below blue line, get further crossed up, add further drag and loose the plot.

Once in the air an aircraft does not know that it is at 300 feet or 1000 feet and mayb in certain situations it might be better to go for level flight at 300 feet rather than the drummed in climb. Most airfields are not enclosed by high terrain and usually have a gentle turn route through where you can maintain level flight at your 300 or 500 feet. Once trimmed for level flight and at single engine cruise speeds step climb the twin in gentle increments using the trim. As the cruise speed bleeds off level again and repeat until you have sufficient hight to return or land at another airfield.

ThIs does work and while not suitable for all situations it is another option to consider if you get into a mess.
It is certainly worth trying in training with a safety pilot/ instructor and at altitude.

Pace

[Wizofoz]

Blue line is the best climb speed on one engine. How is climbing, however slowley, better than maintaining altitude?

[Pace]

>Blue line is the best climb speed on one engine. How is climbing, however slowley, better than maintaining altitude?<

Because you may not be climbing at all at blue line and without speed your margins are smaller and it is easier to get below blue line with all the horrors of increased drag and a dramatically worsening situation which shows up in the appalling twin accident rates with one engine out.

But I am NOT putting this forward as a replacement to blue line climb but an extra alternative in certain situations. Go try it in a safe situation and make your own mind up.

Pace

[Wizofoz]

Because you may not be climbing at all at blue line

I do see your point Pace, but the physics don't add up. It sounds a bit like the old "Getting it over the step" myth.

If you aren't climbing at blue line speed, i.e you are only just maintaining altitude, then you are using all the available power. If you don't have excess power to climb, you also don't have excess power to accelerate. If you DO have excess power to accelerate, you are always going to ALSO have excess power to climb.

What you seem to be getting at is keeping some extra margin over blue-line to alow for gusts etc. Fine- but holding a constant speed just above blue-line is going to be more efficient and give you a better net flight path than the "saw tooth" flight path you seem to advocate.

Unfortunatley there are no free lunches in physics- either the power is there or it isn't!

[fireflybob]

Interesting question - are there any hard statistics for this?

One way of solving the asymmetric problem is to close all the throttles! Ok you become a glider then but at least you are under control!

One thing the BA777 at LHR proved is that if you are going to crash then keep the wings level and don 't stall!

Your question only considers the take off situation. There are other occasions where it's nice to have two engines - flight over water or inhospitable terrain and/or night or IMC!

Reminds me of the definition of the ideal a/c when the engineer taps the captain on the shoulder to tell him "We've lost number 4" - the Captain replies "Which side?"

Ok yes light twins can be challenging but on balance I would rather have another engine. There are also aspects such as having 2 alternators and 2 vacuum pumps which mean more redundancy.

It would be interesting to know how many accidents have been prevented because the type was a light twin and not a single.

[Pace]

>If you aren't climbing at blue line speed, i.e you are only just maintaining altitude, then you are using all the available power. If you don't have excess power to climb, you also don't have excess power to accelerate. If you DO have excess power to accelerate, you are always going to ALSO have excess power to climb.

What you seem to be getting at is keeping some extra margin over blue-line to alow for gusts etc. Fine- but holding a constant speed just above blue-line is going to be more efficient and give you a better net flight path than the "saw tooth" flight path you seem to advocate.

Unfortunatley there are no free lunches in physics- either the power is there or it isn't!<

Wizofox

But it is Physics and there are no free lunches as you put it but the wrong way. With one engine out in a climb you have drag that you do not need to have. You have extra drag from a higher angle of attack on the wings and the slower you are the more rudder you will require to combat the yaw.
Its all a vicious circle.
By reducing the pitch you are reducing the drag and hence the aircraft will make the most of the available power and accelerate as it accelerates less rudder sticks out in the airstream.

On a hot day at Grosse weight your other engine might be there to carry you to the crash site. Before you make a forced landing this trick might work. As I Said go try it as its another option up your sleeve before taking to the trees.
And yes it is all about Physics so please do feel free to pull the Physics apart because it is for discussion.

Also remember we are always playing with available power and drag but we always have another source of extra power, an extra engine if you like and that is the kinetic energy inherant in the aircraft by using pitch or your
control column.

In a single engine aircraft with the engine out you have only that spare engine (kinetic energy) to maintain your speed to a forced landing. Instead of your throttle controlling your power. Your control column becomes your throttle and you are trading altitude to get that energy

Pace

[radicalrabit]

B52 by any chance?

[Pace]

>Your question only considers the take off situation. There are other occasions where it's nice to have two engines - flight over water or inhospitable terrain and/or night or IMC!<

Fireblob

This is my point. You loose an engine in the cruise and its no major deal to shut it down and fly for miles on the remaining engine the plane does not know whether its at 4000 feet or 400 feet and behaves roughly the same.
But the same plane asked to climb? and you are in a totally different ball game.

Pace

[Pace]

RadicalRabit

No this is a serious point for discussion. I have over 2500 hrs in light twins alone and your welcome to my ATP numbers to a private E mail.

Pace

[Genghis the Engineer]

Whilst agreeing that the single engine performance of most light twins is very poor, I'd be interested to see your accident statistics backing up the initial premise - I'm usually quite on top of the accident reports and don't recall seeing many, if any, reports of losses of light twins following single engine failures.

G

[411A]

All this talk about light twin accidents being 'attrocious' quite frankly is without hard facts.
In the USA, the accident rates for single and multi-engine airplanes are about the same.
However, what you don't hear about (nor reflected in statistics) are most of the multi-engine airplanes that have an engine failure enroute, and land just fine, thank you very much, at an airport.

Singles?
Usually make the news, simply because when the engine quits, you either find an airport (usually doesn't happen) or end up in the weeds somewhere.

The NTSB accident reports are there for all to read...and learn.

Of course, in other countries...could be totally different.

[airfoilmod]

No losses of aircraft (light twin) after OEI? Pretty bold statement, Sir. I know of two in my circle of aero alone. I'll check some more for you.(411: "atrocious" is in the eye of the beholder, your call isn't the Cessna 411? One would hope)

Airfoil

[Wizofoz]

Pace,

Drag is made up of form drag, which increases as the square of velocity, and induced drag, which does indeed increase with angle of attack.

This is where we come up with the drag curve, where drag is minimum at a particular speed/angle of attack, and increases with EITHER an increase OR decrase in speed or angle of attack.

Vyse ("blue line" speed) is speed for maximum excess thrust on one engine, but is very close to the minimum drag speed. You are correct that drag from control inputs are a factor, but are included in the flight test data to determine Vyse.

By reducing the pitch you are reducing the drag and hence the aircraft will make the most of the available power and accelerate as it accelerates less rudder sticks out in the airstream.


Yes, but if you reduce "pitch" (I think you mean angle of attack- there is a difference) before you accelerate, you also reduce lift. If you were only maintaining height at Vyse, you are now descending. Sure you'll accelerate, but, as I said above, as you were at your minimum drag speed before, flying faster is only going to increase total drag and make things worse.

The blue radial is there for a reason. It really is the speed for best climb performance on one engine.I have a similar amount of light twin time as you (though a lot of years ago!) and I know that sometimes equates to "Not very much!!", but it is the best you are going to get. Fly any other speed, faster or slower, and you degrade the aircrafts climb performance.

[gr8shandini]

I think I understand what he's saying. He's not saying that nosing over will find you some extra power you weren't making before, but rather assuming you've got a small but positive rate of climb, so you do have excess power available by definition. Therefore it is conceivable that you might be able to reduce your workload by trading a climb that really isn't getting you up very fast for a little extra airspeed so long as you're above the surrounding terrain. Obviously, if you weren't climbing a Vyse, this would go right out the window.

However, I think the improvement in handling qualities would vary from aircraft to aircraft depending upon how wide the spread between Vmca and Vyse is and the few extra knots you gain might not be worth it.

[Telstar]

I remember reading a very intersting article in one of the big General aviation "Comic books" when I was going my initial ME rating, written by one of the well knwon gus, whos name escapes me now.

Up to that point I had read all the material the good people at Jepps and the FAA had written on dealing with Engine failures shortly after takeoff, as well as my instructor. Essentially, get it cleaned up, and climb away at Blue Line.

The author of this article stated that Comair, who started out in life operating only light twins such as the Navajo had suffered serious accidents as a consequence of Pilots loosing an engine, and tring to climb away at blue line, but due to the face that they were nearly always at MAUW and in hot conditions or high locations, had resulted in speed decaying and loss of control in flight at low levels.

Their revised policy was this:

Engine Failure from 0ft-500ft, close throttles, land straight ahead.

500-1000ft Close throttles land ahead, with turns of up to 40 deg left or right

Above 1000ft Attempt to climb away at blue line.

The reasoning was that it was far more likely to go below VMC and violently loose control at low level resulting in a large smoking hole, then to have a more then likely survivable forced landing under control.

I only did about 15 hrs Multi Engine Piston and I fly Jets now, but I often wonder still, if I had found myself in that position would I have gone with conventional wisdom or the other option. Pardon my ignorance.

[Pace]

>Yes, but if you reduce "pitch" (I think you mean angle of attack- there is a difference) before you accelerate, you also reduce lift. If you were only maintaining height at Vyse, you are now descending. Sure you'll accelerate, but, as I said above, as you were at your minimum drag speed before, flying faster is only going to increase total drag and make things worse.

The blue radial is there for a reason. It really is the speed for best climb performance on one engine.I have a similar amount of light twin time as you (though a lot of years ago!) and I know that sometimes equates to "Not very much!!", but it is the best you are going to get. Fly any other speed, faster or slower, and you degrade the aircrafts climb performance<

Wizofox

Yes I do mean angle of attack :-) I can give you some figures off a Seneca Five. With an engine shut down and feathered it will cruise at 127 kts compared to 155 kts with both going and that is with a high cruise setting not max power which you would have trying to climb at blue line which is about 90 kts.

So we have a difference at a lower power setting of nearly 30 kts.
That difference is purely down to drag nothing more nothing less.

Faster air over the wings creates more lift meaning that you can reduce the angle of attack and hence the drag for a given amount of lift.

In the situation we are talking about where because of tired engines a bug splattered airframe, temps, weight etc where we have max power, blue line and no or negligable climb then yes as we reduce the angle of attack initially the aircraft will start a very slight descent. As the speed increases so does the lift meaning you can reduce the angle of attack even further and even further again as the speed continues to increase to a cruise single engine speed.

As I said do try it :-)

Pace

[Pace]

>The author of this article stated that Comair, who started out in life operating only light twins such as the Navajo had suffered serious accidents as a consequence of Pilots loosing an engine, and tring to climb away at blue line, but due to the face that they were nearly always at MAUW and in hot conditions or high locations, had resulted in speed decaying and loss of control in flight at low levels.<

Telstar

I agree Landing ahead is a last option and I am putting this forward as a further option which can keep you in the air rather than down in the trees. I have tried it and it does work.

If there were good twin accident statistics engine out I would shut up but they are attrocious and to me the training and options trained are not complete for light twins ONLY.

If anyone wants to argue the Pyschics feel free as I am purely opening up a discussion not trying to win points

I am not trying to reinvent the wheel but wonder whether the wheel was totally round in the first place regarding light twin training. The problem could be that historically light twins have been used to train for bigger stuff that climbs at 1000 fpm engine out and the training doesnt look at the light twin on its own.

Pace

[Genghis the Engineer]

AirfoilMod - I don't dispute that accidents must occur since I don't manage to read every accident report in the world and I'd be amazed if there aren't some SEI related accidents. But are they really significant in the global scheme of things - that is compared to other accident causes, or for that matter in terms of engine failures causing accidents when they do occur? I'm happy to be convinced, but I've not seen the stats to do so.

G

[Wizofoz]

Faster air over the wings creates more lift meaning that you can reduce the angle of attack and hence the drag for a given amount of lift.



By any chance do you mean that L= CL*1/2 rho*V>2? Cause it does.

If what you said above were true, then the faster you went, the less total drag you'd produce, and the aircraft would just keep accelerating until it approached the speed of light! Congratulations, you've just invented perpetual motion and solved the universes energy crisis!!

Induced drag is one side of the story. On a typical light aircraft it reduces to near its minimum value at about 5deg A of A, and peaks at CLmax, which is to say stalling angle.

But as speed increases, so does form drag.

Tell me, if you put your hand out the window of your Seneca at 127kts as opposed to 90 kts, at which speed would you feel the most drag? That's called form drag which, as I explained, increases with velocity. Do you dispute this?

So, you have one form of drag that INCREASES with speed, and one that REDUCES (though, after a while, only by a little). At some point, the sum of these two values is at a minimum, and that is Dmin, which is very close to Vyse.

Hav a look here:- http://selair.selkirk.bc.ca/aerodynamics1/Drag/Page9.html

Your Seneca may be able to maintain a Tas of 127 at altitude, but it won't sustain a climb at that speed. The maximum sustained rate of climb occurs at a particular speed, and the nice guys at Piper even put a blue radial on your ASI to let you know what it is.

[Pace]

By any chance do you mean that L= CL*1/2 rho*V>2? Cause it does.

>If what you said above were true, then the faster you went, the less total drag you'd produce, and the aircraft would just keep accelerating until it approached the speed of light! Congratulations, you've just invented perpetual motion and solved the universes energy crisis!!

Induced drag is one side of the story. On a typical light aircraft it reduces to near its minimum value at about 5deg A of A, and peaks at CLmax, which is to say stalling angle.<

NO because at the end of the day the airframe is pushing through air and there will always be a terminal velocity for given power. Hence even a sky diver will hit a terminal velocity. As you know the higher in the atmosphere the faster you go.

>If the BEST rate of climb is zero, flying any other speed produces a descent.<

Yes if you have 90 kts and blue line and you are only staying level any reduction in the angle of attack will result in an initial decent and an increase in airspeed as Kinetic energy comes into play and assists the energy produced from the engine. But then as airspeed increases the lift increases for a reduced angle of attack and the descent rate will reduce until as the airspeed increases further you will finally achieve level flight at single engine cruise speed.


The same as pushing a wooden spoon through custard and water and a wooden spoon isnt a wing and neither is the sky diver.

I am fully aware of other forms of drag and your theories on how blue line is calculated for single engine climb. But as you know only too well at best lighttwins do not climb very well and at worst dont at all, You are also very close in speed to where if you get below blue line the drag increases dramatically and that is the killer.



Pace

[gr8shandini]

Pace:

Sorry but the Wiz is right on this one (but never mind the man behind the curtain! - sorry, couldn't resist). When you do flight test to determine Vy, you do climb testing at various airspeeds and construct the total drag curve shown in the reference he cited. The bottom of that curve is Vy and it gets published in the books. Vyse is determined in a similar manner with one engine out which automatically takes into account the added drag of using rudder to counteract the yaw moment. So there's no way to reduce drag by deviating from the blueline speed. Hence, if you're not able to climb at Vyse, reducing your AOA is going to result in a loss in altitude that you will not be able to regain. Not a good situation.

However, what I think your fighter jock friend was getting at is that for many airplanes, the bottom of that curve is rather flat. That means that if you have a little excess power available (i.e. a positive rate of climb at Vyse), you might be able to gain a significant amount of airspeed if you level off. But this effect can - and probably does - vary quite a bit between aircraft. On some it might work great. On others, it might not be worth it. Therefore it's not something you could teach folks to do unless you were willing to submit to requiring a type rating each aircraft.

[Wizofoz]

Thanks Gr8, There"s no place like home!!

Pace,

One big difference between Skydivers (1200 jumps and an AFF rating, just by the way!!) and aeroplanes is that skydivers don't have engines!! Aeroplanes don't have "Terminal velocities". They accelerate until the total drag (which, we've established, INCREASES as speed increases at any speed above Dmin) is equal to the thrust.

I think you may be acknowledging that the best performance is indeed achieved at Vyse. What you then suggest, i.e that the problem is that at any speed below that, drag increases, is totally valid. If you have excess performance, indeed it may be wise to use it to climb at a higher speed, thus increasing your margins over the bottom of the drag curve. This will, however, lead to a reduced climb rate. If the terrain makes this acceptable, then it may be fine as a technique.

You did, however, indicate that you believe the aircrafts total drag reduced and performance increased at speeds in excess of Vyse and, I think I've shown, this is simply false.

[Pace]

Wizofox

>One big difference between Skydivers (1200 jumps and an AFF rating, just by the way!!) and aeroplanes is that skydivers don't have engines!! Aeroplanes don't have "Terminal velocities <

Firstly aeroplanes most certainly DO have terminal velocities!!! and sky divers most certainly DO have engines :-) Ok not in the conventional sense but in the Kinetic energy they are using returning earthbound and which was created hoisting them skybound. In the same sense a glider has an engine in its Kinetic energy which was created pulling it skybound and which is on tap to the glider pilot through the joystick earthbound. the joystick is his throttle if you like.

No again :-) Put in simple terms as I am a practical sort of pilot and not a mathematician what do you do if you are holding blue line, you are at 400 to 500 feet and rather than getting a climb your VSI and altitude are going down?

You either panic as do many low time twin pilots and pull back trying to get a climb and go into coffin corner or you put it down hoping you dont take out trees or buildings in the process.

Take my word for it there are many situations as above where the aircraft ends up as a hole in the ground. Hence the bad engine out record of twins.

You also know that while many twins really struggle especially on hot days at grosse weight and blue line does not work in giving you the desired climb or even maintaining altitude.

So you have two choices you either continue trying to get a climb and end up in coffin corner with the usual stall /spin hole in the ground or you close both engines use the kenetic energy( which incidentely was created by the aircraft engines dragging the plane mass to altitude) and become a glider to a forced landing. (using the inherant kinetic energy to control your speed on the way down ie your spare engine as with the Skydiver) :-)

Your other option is to try out what I have said on your next flight. Mathematics or armchair pilot discussions aside it does work. I have seen and experienced the reality of this with my own eyes.

Then when you have tried it come back and explain why.
As they say the proof of the pudding is in the eating

You are missing something in the science or the mathematics here but the clue has to be in the fact that light twins will happily cruise all day on one engine at 127 kts but will not happily climb at blue line in all conditions and that is a practical answer.

Pace

[bookworm]

The rationale seems to be that even if your rate of climb at Vyse is pitiful, with no terrain to worry about it may be better to accept even half of pitiful in return for the better control that a speed above Vyse offers, since fatalities are typically associated with loss of control rather than CFIT. Since the curve is relatively flat, you may manage quite a speed increment without losing all your climb capability.

I can't see the point in step climbing. Surely a sustained, trimmed, shallow climb is preferable, and will return the same or better average RoC without having to flirt with Vyse from time to time?

[Pace]

>I can't see the point in step climbing. Surely a sustained, trimmed, shallow climb is preferable, and will return the same or better average RoC without having to flirt with Vyse from time to time?<

We use that technique all the time in underpowered citation jets at high altitudes. It is again using your jet engine power which is insufficient to maintain an adequate climb and subsidising that power by adding the kinetic energy created in level flight.

While in a citation 2 you may struggle from FL350 and pan out trying to achieve FL370 at a given weight and conditions. You can get up there by allowing the aircraft to accelerate and then use the jet power plus the kinetic energy to give you the climb to FL370

Pace

[PK-KAR]

Twins are not unsafe nor is the accident record terrible... I can attest that if the pilot does what he is supposed to do... if you know what your doing, you will be fine.
So let's all call for an abort after V1, overboost our engines for the sake of getting more runway left if we need an abort, instead of using the shameful derates/flex, and tell the crew to change seats when hanging by the props because of the rotational direction...

Really?

Nice one SSG v4.0... I can't wait for V5.0
---
Another beer Pace?

PK-KAR

[Pace]

PK-KAR >Another beer Pace?<

Is it my round or yours ? :-)

Actually I am getting quite fond of him popping in in different guises :-)

Pace

[PK-KAR]

Sorry mate, I miscounted...
It's v7.0 now... just waiting for v8.0...

At the rate this is going, I'd have liver failure pretty soon!

Oh whaddaheck... Here's another round of beer...

[john_tullamarine]

A few ill-conceived ideas floating around in this thread ..

(a) AEO/OEI, the climb performance graph is something of an upturned teacup profile .. with the AEO picture sitting a long way above the OEI

(b) the actual numbers will depend on the aircraft, configuration, atmospherics, etc

(c) regardless of the numbers, best climb performance is somewheres in the middle .. not at the ends of the graph

(d) typically, in a light twin other than at low weight and Hp/OAT, this OEI best climb performance will be modest .. or negative (ie a descent)

(e) if the aircraft flies slower/faster (presuming same thrust) it will be at a reduced climb/increased descent as appropriate .. you can't make something from nothing

(f) blue line is for one set of conditions and may not be appropriate for the actual conditions (including aircraft in-service deterioration) but it's probably a good place to start unless you have the flight test info to start with a different speed

(g) the problem of letting speed decay trying to chase mythical climb performance ... is one of flight management discipline and airmanship and has a predictable outcome in most cases ...


So far as ssg is concerned .. we will continue to remove posters who show an uncanny resemblance to him ... however, each new incarnation takes a little while to suss out. If it provides a modicum of amusement for the remainder of the folk, so be it.

[Wizofoz]

400 to 500 feet and rather than getting a climb your VSI and altitude are going down?


Pace,

Last post for me as you've proven you're not good at listening.

If, in the above situation you now lower the nose to accelerate (assuming you were at the correct Vyse at the time), your descent will increase and will stay that way. Thus your hole in the grond will be nearer and deeper.

As to "Step climbing" a Citation, if you didn't have the excess thrust to get to 370 in the first place, you won't have the thrust to stay there.

Find me one authioratative text that refers to an aircrafts level airspeed as a "Terminal velocity."

As to being an "armchair pilot", MY armchair is located at the front left of a Boeing 777!

[Pace]

>If, in the above situation you now lower the nose to accelerate (assuming >you were at the correct Vyse at the time), your descent will increase and will stay that way. Thus your hole in the grond will be nearer and deeper.<

So what you are saying is that even at 2000 feet and a blue line climb with no climb. If you reduce the AOA and increase speed you will descend all the way to the ground from 2000 feet?

>As to "Step climbing" a Citation, if you didn't have the excess thrust to get to 370 in the first place, you won't have the thrust to stay there.<

Again step climbing is used by many citation pilots where the climb rate is so low that the only way you can stop it going on the back of the drag curve is to allow the speed to increase, lower the angle of attack and use the kinetic energy to assist that last bit of climb. As you level and the aircraft accelerates and angle of attack reduces so does the drag making the available thrust sufficient.
At high level the gap between the Ias and stall is small and yes there will be a level where to maintain that gap you would start sinking.
It is not just about available thrust its also about AOA and drag.

>Find me one authioratative text that refers to an aircrafts level airspeed as a "Terminal velocity."<

Every object will have a terminal velocity

[Pace]

Wizofox

Rather than point scoring over each other I would rather leave it with you and beg to differ. You will not change my opinions and I will not change yours.
All I will say is that the accident rate is very poor for engine failures on Light twins and that is an unacceptable state. So something has to be wrong somewhere?

All the best

Pace

[frontlefthamster]

We all know that the accident rate for light twins is attrocious with an engine failure.

Infact I believe you are more likely to survive a single engine failure and the subsequent forced landing than an engine failure in a twin.


This sort of 'statistic' surfaces from time to time...

The fact is that following engine failure in a twin, providing the subsequent landing is safe, there will be no formal 'publicity'; the event is non-reportable and will not be investigated. Thus the numbers are slewed - all the published reports you see relating to twins with one engine out are accident reports, because something has gone wrong.

The assertions above are simply rubbish. Even if you wanted to prove them, you couldn't, because there are no statistics to help you. Many engine failures occur in light twins, and end in safe landings on proper runways.

[Pace]

>The fact is that following engine failure in a twin, providing the subsequent landing is safe, there will be no formal 'publicity'; the event is non-reportable and will not be investigated. Thus the numbers are slewed - all the published reports you see relating to twins with one engine out are accident reports, because something has gone wrong.

The assertions above are simply rubbish. Even if you wanted to prove them, you couldn't, because there are no statistics to help you. Many engine failures occur in light twins, and end in safe landings on proper runways.<

FrontLefthamster

You may have a valid point and it would be nice to see those statistics and how they arrive at them?

But fair dues a pilot of a light twin always has the option of closing both down and treating it as a forced landing.

That is the difference the second engine gives you more options than in a single my suggestion was another further option to have up your sleeve.
If that still doesnt work close them both and take your chances with what lies ahead. Your not loosing anything and it does work science or no science.

Pace

[Wizofoz]

Pace, the difference is that I am stating facts, not opinion.

Best rate of climb, single engine is just that. Minimum drag is just that. Maximum altitude is just that. You claim to somehow magically be able to make an aircraft climb at BETTER than BEST rate of climb by achieving LESS than MINIMUM drag, and climb to HIGHER than MAXIMUM altitude.If that's the case, Boeing needs to talk to you now!!

[Centaurus]

The problem is not so much the marginal rate of climb following an engine failure shortly after take off, but the failure of the pilot to take instantaneous corrective action including the feathering procedure. The flying schools teach an often inappropriate lengthy period of identification via various methods, and often critical seconds have gone by the time the pilot gets around to actually feathering the propeller.

A generic drill mouthed by the pilot may include identification of the failed engine by the direction of initial yaw (dead side - dead leg etc). Then a careful check of the engine instruments to confirm the cause of the initial yaw. Then a further confirmation takes place by slowly retarding the throttle of the suspect engine. All this time the colossal drag of the windmilling propeller is taking steady toll of airspeed and within literally seconds the airspeed has dropped 10-15 knots from the initial engine failure figure.

The fact is the feathering of the propeller must take place immediately after the engine failure is detected in order to stop the danger of speed decay. The risk of closing down the wrong engine must be balanced against the certain potentially fatal loss of airspeed that will occur unless the dead engine is feathered without delay. The act of closing the throttle of the suspect engine as a means of confirmation, raises the question of how fast do you close that throttle lever. It is generally accepted as a slow movement just in case the wrong throttle has been closed and you don't want to momentarily lose all power (wrong throttle pulled back and dead engine already dead equals a problem!).

A slow pull back of the suspect engine loses more precious seconds of windmilling drag and thus decaying airspeed. To competently handle an engine failure after take off at low altitude requires instantaneous correct feathering action without the luxury of "dicking around". This way, the danger envelope of windmilling drag is minimised to perhaps around 5-8 seconds. But to arbitarily state the pilot should deliberately close both throttles and crash straight ahead simply because the altitude is less than 500 feet when an engine fails, is shutting off all options that may have been available.

[Pace]

>Best rate of climb, single engine is just that. Minimum drag is just that. Maximum altitude is just that. You claim to somehow magically be able to make an aircraft climb at BETTER than BEST rate of climb by achieving LESS than MINIMUM drag, and climb to HIGHER than MAXIMUM altitude.If that's the case, Boeing needs to talk to you now!!<

Wizofox

Yes I appreciate best rate of climb single engine. I appreciate Minimum drag at best rate of climb BUT I am not talking about climbing at all or minimum drag in the climb.

The reason I am NOT is the very fact that even with new aircraft where the miserly 200fpm are achieved on standard days, Many light twins may be 20 years old, be covered in hanger rash, have tired engines and the temperatures may be above standard.

Most light twins quote 200 fpm as new test aircraft, some not even that. So the point is not to climb at all but even low level to go for a single engine cruise.

With any climb you are looking at an increase in angle of attack and with an increase in angle of attack you are looking at DRAG.

Remove that drag and as I stated as fact a seneca will accelerate to near 130kts on one engine in a level cruise. Push the nose over and that 130 would increase as the aircraft traded altitude for its inherant kinetic energy.

Drop below blue line and you are into coffin corner as the drag increases dramatically and that is where the margins are very small.
The guy who does everything right establishes blue line, has the aircraft clean and still has no climb or even a descent has two choices one is to close both throttles and glide to a landing ie using kinetic energy alone to control his speed to a landing or he can reduce the drag of a climb and set up a level cruise.

Its not Magic but pure fact that a light twin will cruise for hours happily with one shut down but will not climb happily with one shut down.

The step climb works on the fact that you are dipping into Kinetic energy to add to the available power from your engine and gain some altitude.
I will give an example from the seneca.
You have one engine running your speed in level flight is 127kts (fact) you are not going down but level. Now you pitch for a climb. You still have the power of that one engine which is constant but you trade some speed for extra climb. As you pitch up the drag increases and the aircraft is now climbing with the constant engine power plus the kinetic energy. What happens is the speed starts to decay but you get a greater climb rate than you would at blue line. Allow the speed to decay from 127 kts to say 105 kts and then pitch for level flight again maintaining altitude. Slowly the speed will increase. when you are back to 127 kts go through the process again.

All I am saying here is make the plane do what it can happily do ie fly level not climb. If you cannot see that I really do not know what to say Other than I will beg to differ with you these are facts not suppositions and I am happy to demonstrate to you any time. If I am right you pay for the flight if I am wrong I pick up the bill.

Pace

[PK-KAR]

The reason I am NOT is the very fact that even with new aircraft where the miserly 200fpm are achieved on standard days, Many light twins may be 20 years old, be covered in hanger rash, have tired engines and the temperatures may be above standard.
It can become 50fpm before you know it... if you're lucky... and that's before OEW revisions...
Whenever we got one engine out on take off, I have to rush back to the hotel and pick up clean underwear... not too often, but you know what I mean.

At 33C, we're often reduced, because otherwise, we'd be forced to do what Ssg does on N-1 at anywhere during the take off, abort... I refused a "symbolic" V1 for the ops... reduce the load thank you! The first time I saw that light twin do a near MTOW run after maintenance, the engine conked out and 3000m runway suddenly looked very short!!!!! (thanks to a former CASA/MDCA guy who advised we avoid MTOW citing reasons Pace mentioned).

For ref: It was a C402B, a DAMN OLD one... :}:yuk::ugh:

PK-KAR

[Wizofoz]

Pace,

We are actually closer to agreement than you recognize, at least in terms of technique. Flying level at a higher speed rather than climbing slowly at Vyse may indeed have merit as a technique where terrain is not a factor.

What I am NOT willing to let you go on is some of your more outrageous errors when it comes to aerodynamics, as they have led you to make statements that work only in the magic kingdom.

Your statement:- I appreciate Minimum drag at best rate of climb BUT I am not talking about climbing at all or minimum drag in the climb. and then say With any climb you are looking at an increase in angle of attack and with an increase in angle of attack you are looking at DRAG. Shows that you neither appreciate or understand a fairly basic concept.

Minimum total drag occurs at a particular angle of attack, which, at a given weight, will correspond with a particular speed. Whether you climb, descend or stay level at that speed depends on how much power is applied. You continue to imply that accelerating , because it lowers the angle of attack reduces drag. It REDUCES induced drag whilst INCREASING form drag, thus INCREASING total drag. Minimum means minimun, anything else is an increase.

Vyse is not exactly Min drag, but it's close, as it takes into consideration things such as control drag. BUT it is the BEST RATE OF CLIMB SPEED and thus, by definition, any other speed has LESS rate of climb (Look BEST up in the dictionary!). If the BEST rate of climb is zero, flying any other speed produces a descent.

Go ahead and and fly level all day. As I said, it may be resnoble under some circumstances. Just don't imply you can somehow make an aircraft do BETTER than BEST!.

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!!

[On speed on profile]

When I flew twins off a reasonable runway, 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 I didnt have to worry, I would just put her back down on the runway if I needed to and once the gear was up, I was gauranteed a climb with a healthy margin above blue line until about 1000' AGL where I could level out and asses the situation. My reason for flying like this was for the exact reason PACE asked the initial question. To keep a healthy speed above blue line!

Bear in mind, this option isnt advisable on a short runway!

OSOP

[Pace]

>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

[gr8shandini]

Pace,

Check out the following site:

http://selair.selkirk.bc.ca/aerodynamics1/Multi/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.

[Wizofoz]

But you are reducing drag by reducing AOA

We're close, Pace, but still not there. As I've said, Vyse is not exactley minimum drag speed, but it is towards the bottom of the drag curve. Fly at any speed other than minimum drag speed and drag INCREASES.

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!!

[Pace]

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

[Wizofoz]

All I will say about these Graphs is that they are designed for engine out CLIMBS

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.

[Pace]

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

[Wizofoz]

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.

[Centaurus]

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

That certainly is a novel precaution not mentioned in the manufacturer's POH or FM. Pity about all that extra landing gear drag wheels down while attempting to accelerate promptly to a safe singe engine speed. All you have proved with your "technique" is to place the aircraft further along the runway when you decide to cut both throttles and land straight ahead on the remaining length.

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.

[Pace]

>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

[Wizofoz]

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?

[411A]

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.

[Pugilistic Animus]

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:(

[Brian Abraham]

BRING BACK THE MAYTAG
What? The P-51? (Known as the Maytag by some during WWII since Maytag were very skilled at casting aluminium and made many of the castings on the 51). Sorry for the OT. Pace is not Angels 60, cattleflyer et al in another disguise? Perhaps they're just friends.

[Wizofoz]

Thanks Guys!

Yes, the forhead has been getting a workout on the wall here!!:ugh:

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!!

[airfoilmod]

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?

[mark sicknote]

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:ok:

[FullWings]

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...

[Pace]

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

[Pugilistic Animus]

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:ouch:

no se lode a nadie

PA

[Pace]

>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]

in a WAT limited FAR 23 twin your NOT trying to climb your trying to do a -shall we say a ''controlled arrival''---nothing is worse than a mishandled twin---except, you can stretch your 'glide' in this case--at Vyse...that's it... no guarantees otherwise---that's far 23

[Pace]

Pugilistic animus

The proof of the pudding is in the eating IT WORKS! and is another option before you take to the trees. You can always still take to the trees if it doesnt :-)

pace

[Pugilistic Animus]

Ok, you're right---let's just erase the First Law---the law of conservation of energy--out of all those muppety physics books and it will work:}

[Wizofoz]

To clear up a few points yes it is obvious that the faster you go the more drag there will be, not in question.

Actually, you have repeatedly said you believed the aircraft produced LESS drag at greater speed because of reduced A of A, and got rather snooty with me when I pointed out that, above Min drag speed, drag inceases.

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.



Absoluttely. Being trying to get that across to you. Now, if the BEST rate of climb is zero, what rate of climb will you get if you fly faster (I'll give you a hint, it starts with a minus sign.)

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.


No, they are NOT climb graphs. They show how much drag is produced at given airspeeds, and therefore how much power is required to maintain LEVEL flight.

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.


Wizofoz has told you several times, and been backed up by several other experienced aviation specialists, that the difference between climb and cruise is that excess power is used to increase speed instead of increase altitude. You boggle at the fact that the amount of power it takes to make a two ton aeroplane climb at 100' per minute will, if re-directed, make at accelerate 25 knot, but that is what happens.

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.



I can't comment on this 'cause I can't work out what the HELL you're talking about!!

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?

Easy, it won't. If it won't climb at Vyse, it won't cruise at any other speed. Simple.

[Brian Abraham]

Pace - scimming through your posts I think you may have a misunderstanding as to what kinetic energy is. Kinetic energy is a form of energy that an object has by reason of its motion. The kind of motion may be translation (motion along a path from one place to another), rotation about an axis, vibration, or any combination of motions. The total kinetic energy of a body or system is equal to the sum of the kinetic energies resulting from each type of motion. The kinetic energy of an object depends on its mass and velocity. For instance, the amount of kinetic energy KE of an object in translational motion is equal to one-half the product of its mass m and the square of its velocity v, or KE = 1/2mv^2.
Bob Hoover looping his twin using nothing but Kinetic energy
leaves cruise thrust set and descends his aircraft will accelerate due to Kinetic energy plus his thrust
Both these statements are incorrect. Hoover maintains the kinetic energy state of his aircraft (speed is the only thing he has control over since its mass is fixed) by using his potential energy, which is the altitude available to him. When Wiz sticks the nose of his 777 down it accelerates because he is using up some of the potential energy available to him by virtue of his altitude. He is trading altitude to increase the kinetic energy of his aircraft (ie speed), but in doing so he is losing potential energy (height).

[Scotteo]

The second engine may also go out while dealing with the first if, for example it is a fuel problem. If this were the case then a pilot will need all the potential energy he can translate.

Yes I agree that adopting the cruise attitude and airspeed would make it things easier but I would prefer to perform a blue line climb just incase the second goes.

[OutOfRunWay]

Im a little confused by all this discussion.

The blue line will give you the most efficient single engine Climb provided you havent modified your aircraft heavily - its been tested to exhaustion by the manufacturer.

If you cant reach the blue line on one engine at your present angle of attack, flatten your climb until you can reach it, and then increase climb to maintain. Do not turn or even breathe before youve reached it. If you have to flatten your climb until you're level to just make the blue line - that is bad.

If you cant reach the blue line even in level flight - that is worse: youre going down; find a good place so as not to bend her too much.

Thats about all there is to it.

regards, OORW

[airfoilmod]

Rather than reducing AoA a little at a time, isn't it safer to establish level flight first, then nibble at a climb? Seems like the proper sequence to me. Allowing for terrain clearance certainly. Level flight isn't necessarily "bad". It is what it is if that's what it is. You're sequentially trying to stay ahead of Stall, rather than chasing it from the safety of green flight.

[Pugilistic Animus]

Brian, I'm too selective---any heaver duty washer shall do, GE..Maytag, Westinghouse---but before I get to that--- I try to sort out all the dry -clean -only in ground school, before they even get to the wash--I'm just a laundry owner:E---and loving it---because I have more fun watching the students hang on to their youtube debating in my class room than my occasional jet jobs--- because -I love myself and I'm special- and everybody likes me---but most important like Lester I don't care!!!


PA--Maytag Man:E:E:E

[Pace]

>Easy, it won't. If it won't climb at Vyse, it won't cruise at any other speed. Simple<

Wizofox

I think I know what you are getting at! If you have max power on the remaining engine, Are holding blue line speed and have no climb then you will not be able to accelerate without loosing altitude. That I accept.

But lets take this further by using a different scenario. You decide to give up and make a forced landing. You shut down the good engine and become a glider to the nearest field.

You now control your speed with pitch. Ie you pitch for speed. You take whatever descent rate that gives to maintain your VREF and whatever profile.
(The 777 forced landing at Heathrow where they landed short both engines out) You now have only Kinetic or (potential energy) to power the aircraft.

Had you kept the other engine going you would have whatever power/energy that produced plus the Kinetic/or potential energy or Mickey Mouse energy or whatver you want to call it in pitching down.

Lets take an aircraft where the manufacturers claim no single engine climb at all ie no VYSE . ie the De havilland dragon rapide. Yet the aircraft will cruise level at single engine cruise if you loose it in the cruise. You say impossible as if it will not climb at VYSE it will not cruise level at any speed above that? So how come?

So we know that engine out like the 777 crash at Heathrow we have enough energy to maintain a VREF but we do not have enough energy to maintain level flight with one engine going if we can accelerate to single angine cruise by trading altitude for speed?

So in your books in that situation ie blue line and no climb at max power on the remaining engine. When you pitch for single engine cruise the speed will bleed back off to blue line?

But if at VYSE it even shows 50fpm you will be fine at a single engine cruise?

I can easely test this on my next twin flight. All I have to do is simulate an engine failure at say 2000 feet for safety (the plane does not know if its at 2000 feet or 500 feet) I then pitch for blue line and reduce the power until I get no climb or descent but maintain blue line.

No matter what I do with pitch looosing altitude in the process to get single engine cruise the aircraft will descend to the ground with that power setting selected?

Ok give me a couple of weeks and I will make a new thread here with the results include pitch angles, speeds, altitude lost etc as this is not what I see real world.

It is easy to google scientific calculations but there is something missing in those calculations as it is fact that light twins will cruise easely on one but will not climb easely on one.

I have shut down and feathered one engine for real on a few occasions at cruise but would not like to do that in the climb.

I for one am not happy with the explanations given here to what I have experienced for real and know to be true. This thread seems to be full of ego massaging and point scoring rather than a desire to get at the truth. I am happy to back down if I am wrong but as yet???

Pace

[Pugilistic Animus]

AND if you attach a rocket you could climb SE at VN:mad:E, if you please, but You'll need a huge twin tail:}


Lester:E

[Pace]

Pugilistic Animus or Lester

Another intelligent answer :-)

Said with humour :-)

Pace

[Pugilistic Animus]

yo jamas sufro:}

[Wizofoz]

Please do Pace.

Set yourself up on one, then reduce power so you are only holding altitude at Vyse. If you are light this will be a few knots below blue line (which is Vyse at MTOW), so experiment to find the speed which allows you to maintain height with minimum power.

Now, with that power set, do your bunt manoeuvre. You will have a height loss, a temporary increase in speed, but then, to maintain height, you will indeed bleed back to your min power speed again.

Next, set that same speed up and put in enough power for, say, a 200' per min climb. Now level off (no need to lose height) and accelerate to SE cruise. It will be a substantial increase in speed.

The error you are making is in your concept that the aircraft is somehow "Helped" by having more kinetic energy. The ONLY source of energy in a powered aircraft in level flight is it's engines.If it only produces enough power to hold level flight at minimum speed, that's the only energy you have. You can tap the potential energy of your height, but once it's gone, it's gone. Your increased kinetic energy is then robbed by the increase in drag because of the higher speed.


By the way, the Dragon Rapide would not maintain height in single engine cruise OR climb.

[Wizofoz]

Pace,

I'm going to just add one thought here to try and get the point across.

Do you agree (assuming our relationship is amicable enough to allow me to ask questions!!) that an aircraft which is not climbing or descending is flying level?

So, we are dealing with an aircraft that is in level flight with full SE power at Vyse (and, let's face it, that's BETTER than some light twins will do!!).

You are then suggesting that the same aircraft, with the same power, will ALSO fly level at some different, higher speed. You initially seemed to indicated you believed this was because the aircraft produced less drag at the higher speed, but now seem to concede this is not the case, so how do you believe this is possible?

Can you, in your Citation, fly at two different level speeds for the same power settings? Don't think so.Why should a twin on one be any different?

[Pace]

Wizofox

Of course we are amicable :-) i will run these tests but yes I think I will get the results that you are indicating as I have always had a climb at VYSE when going level and it may have been my interpretation which has been wrong ;-)

Addendum

This nevertheless does not negate going for level flight as another option for these reasons.

Firstly in the climb at VYSE your margins are small ie get down draughts, turbulence, distractions, poor piloting skills and it is very easy to loose that target speed and start going into coffin corner. Less speed, more control inputs more AOA, more induced drag and no speed safety margins.

While I appreciate that you cannot create speed if you are only flying level with max power at VYSE, if you do get a climb even a small climb that can be exchanged for cruise speed by leveliing off. With that extra speed in level flight your controls are not all crossed over. You do not have as much aeleron or rudder in put. You do not have such a dead feeling unresponsive aircraft.

So with minimal climb converting that to level cruise is a much more comfortable situation with more margins for error. As your speed builds to say 125 kts in cruise use the trim wheel to climb.take a taget speed well above VYSE say 105 kts allow the speed to bleed off in that climb until it comes back to 105 kts then trim forward again for level flight. Allow the speed to build again to 125kts and again trim for a kinetic energy assisted climb again.

I wish someone would try this and report back as it is a lot more comfortable in a light twin and I believe has less room for error and hence the high engine out accident rates using conventional methods in low performance twins.

Take care

Pace

[OutOfRunWay]

I see what youre getting at. Yes of course, you are correct. If I was doing a practice single engine climb from, say, 1000 ft I would do exactly that: stable in level flight first, and them try climbing and see what happens.

In fact I remember doing just that in days past, and even using a speed slightly higher than blueline specially if it was slightly bumpy, because I knew that if you got too slow, much bad karma would result. (To be honest, engine out on a light twin prop is just not a nice feeling, even if you can get 500ft/m on a plane which isnt heavy)

In a real failure on takeoff, I would however not do that. Chances are that there are trees rushing at you, and you must get air between you and the ground ASAP. That means blue line (or because I'm chicken, slightly faster).

Wizofoz, you are right, in fact I think NO light twin can maintain level at a higher altitude, if it is not almost empty. If you want to cross mountains at say, 16000 ft, you must plan very carefully so you know which way to turn at what point, if one engine gives, and you need to drift down at 150-200 ft/min.

regards, OORW

[Wizofoz]

Cool Bananas pace, we seem to be in heated agreement!!!!:ok:

[Pace]

Wizofox

With your expertise we got there in the end :-) Now I am off thurs to Florida to ferry a Citation S2 back to the uk so will be out of the loop until Sunday after tomorrow. I can even play around with step climbs or energy climbs at high level but with a reasonable climb on both to get level cruise to step ;-)

Pace

[pilotbear]

If you are flying at blue line on your ASI on anything other than an ISA day at MAUW you are flying too fast and will not get the best rate of climb.
You should really calculate the new blue line speed before you go as part of your perf calcs. It can be as much as 10% different.
eg

MAUW = 3000lb and Vyse = 88kts

Actual wt = 2000lb

new Vyse = Old Vyse x sqroot(Actual wt/MAUW)

new Vyse = 88 x sqrt (2000/3000)

new Vyse = 88 x 0.8

new Vyse = 71kts

so if you fly at 88kt you have speed in hand therefore climb rate in hand

[Pace]

Pilot Bear

That also has some important safety factors involved. The pilot who pitches for blue line and doesnt get a climb is going to be fooled into thinking he is in a worse state than he is because blue line would realistically be below the figure he is slavishly transfixed with.

It is also relevant to trying to fly level at blue line with no climb and max power on the live engine.
Because its a speed above the true blue line speed infact the aircraft should fly level? or am I missing something again :-) because if it was flying the true blue line then there would be a positive climb.

But 71 KTS would take quite a bit of courage to go for and there would be so little airflow over the controls just imagine how much rudder and aeleron you would need for a given effect " yikes"

Pace

[Pugilistic Animus]

Any change that depends upon {wate}---:} the new stall reference speed can be---computed by that equation Va/ Vsnew... From Vs---Believe it or not Cessna/ Piper Beech-- Actually knew that:hmm:---but they looked at [perhaps the drag curve...perhaps?????? other STABILITY issues-;)----a nice Vmc/stall--s'il vous plait??:}
INGIUNIRS---THOSE STUPID MUPPETS:}

Lester:E



Y AQUI ESTOY, ESSSPEERANDO POR TI---SI PODER ENTENDER----UNA VEZ MAS

[Pugilistic Animus]

With your expertise we got there in the end :-) Now I am off thurs to Florida to ferry a Citation S2 back to the uk so will be out of the loop until Sunday after tomorrow. I can even play around with step climbs or energy climbs at high level but with a reasonable climb on both to get level cruise to step ;-)

Pace


Ooh Yes --I love playing with engine flameouts and deep stalls---:}

[Pace]

Pugilistic Animus

That was a joke :-) but yes I am ferrying a Citation S2 Florida to UK tomorrow thurs and now look as if I have to carry on down to South Africa so you will have the best part of a weeks relief from me :-)

Then we can start a new topic " does throttle control speed or does pitch?

And the joke was " Student on first solo sitting on the runway pumping his elevator up and down. The instructor called on the radio and asked what the hell he was doing? The student said "well you told me pitch controlled speed and I am pumping the elevator up and down to accelerate" ? Think about it? :-)

Pace

[Pugilistic Animus]

Wolfgang Langweische's "Stick and Rudder" explains those little conundrums exceedingly well:ok:


Power=altitude
Pitch =Airspeed
Rudder [ on an SE] covers the mistakes of those idiot Injunirs:}

[Wizofoz]

Always debatable, but the way I look at it:-

If you're high you have to adjust Power and Attitude
If you're low you have to adjust Power and Attitude
If you're fast you have to adjust Power and Attitude
If you're slow you have to adjust Power and Attitude

So, arguing about which does what is kinda pointless....

Power PLUS Attitude= Performance.

[gr8shandini]

Power PLUS Attitude= Performance


That sounds like a lind from a car commercial.

[busidriver]

Nope...

Power plus attitude MINUS DRAG equals performance

FACT

[Pugilistic Animus]

Power=altitude
Pitch =Airspeed




---which represents [in steady level co-ordinated flight] the vertical and horizontal component of AoA---- which controls lift which equals the wate---but induces drag that needs to be countered by thrust at some finte velocity=power so that forces fore always = forces aft---------:ouch:


PA

[ARINC]

slight creep...but, Why exactly do CAA EASA etc...have such a problem certifying single Turboprop for pax ops with it's associated high MTBF and yet are quite happy to accept the status quo on what statistically has been shown to be higher risk piston twins.

[Wizofoz]

busi,

And which control do you have to adjust the drag???:confused::confused:

If you want a particular performance, you set a power and an attitude. The drag takes care of itself (unless we're talking speed brakes, which we're not!!)

[Pace]

Wizofox we are one on this / made my first part of the trip back florida up to goose bay. Then made it direct to Iceland. Got some good shots of greenland from FL390 but bad turbulence unforecast jet stream of 330/160 kts and greenland to Iceland had OAT of -25c at FL390 so poor performance. Back in the uk Today Sun and then off to South Africa with the S2 Citation tomorrow.

Bought a new camera so should get some nice shots enroute. First stop tomorrow is Morroco.

The S2 is much better than the citation 2 with better climb more fuel 5800 ibs compared to 5000 on the two and can fly for 5 hrs at high level.

Be back frid this week.

Pace