Cessna 340 - lookin' for advice...

[lostpianoplayer]

I've posted this on D&G, my usual hangout, but throught I might trawl here too, just in case...


OK, so I done gone and done it again. Bought another toy. (Reckon I'll get my internet disconnected after this :) A very nice Cessna 340 is being added to the fleet, initially in the US, and then back to NZ. Yes,it checks out very well mechanically, and yes, it's very well priced, given the twin market. I know there's a lot of wisdom here, so thought I'd ask if anyone knows much about these questions:

1. Short field ops. I know, I know - it's not possible, per se, and it's sure not a short field machine. Still. Anyone know what the shortest possible/reasonable/safe takeoff would be for a 340 operating at very low weights? Say, 2 people and 40 gallons/250 pounds fuel. Published take off is 1600 feet or so, but that's at full gross, without VGs, and (I think) involves waiting till the machine is at 90 knots or so before rotating. Anyone with real world experience able to answer this one? A related query is:

2. If you take off at the slowest possible speed, in a fairly powerful twin, is it true that a catastrophic engine failure means you could get into a VMC roll even if you had perfect reactions, in terms of pulling both throttles and applying full opposite rudder? A very experienced instructor and friend of mine says this is the case. He has a lot more experience than me, but still, I'm surprised. I'm willing to "pull the other one" and accept whatever I get if I have a low speed engine failure on take off, but was surprised to hear that no matter what, I'll be heading into the trees upside down. What do you guys think? Is my instructor friend correct?

3. Training. Amongst other machines, my current twin is an old Aztec. The 340 is, of course, a big step up. I can and probably will train in the US. Is Flight Safety (Kansas/Long Beach) overkill? What's a sensible expectation re syllabus and training time for the transition? I'm not looking for shortcuts here...but I'm only VFR, and I wonder if FS's training is skewed too much to IFR?

4. Getting her down to NZ. Am thinking, to be conservative, that the wisest thing to do is take the wings off and pack her into a 40 foot container. Anyone know a. how much of a big deal it is to de-wing & pack such a big aircraft (is it even possible??) and b. contacts for 40 foot containers & shipping from US to NZ?? Of course, a good contact for shipping US to Oz would be fine, cos I'm sure they can get a big box to our little country too...

Any help and all thoughts would be welcome. If anything I've said sounds dumb, well, I guess I'll find out soon enough - but would appreciate the thoughts of them what know...

[B2N2]

In a twin rotation speed should not be below Vmc, therefore:

1. A short field take off in a twin is limited by the acceleration to Vmc ( plus safety margin, usually +5kts or even +10kts)
In a single the shortest possible take-off is actually a combination between the soft field T/O technique and the short field T/O technique.
You can't (shouldn't) do this in a twin. It will lead to lift-off below Vmc.
So the ground roll in a twin is affected by:
-weight
-density altitude (if non turbo)
-runway surface ( dirt, gravel, grass or concrete)
-runway slope.

2. YES.
The definition of Vmc under FAR 23 :

".........critical engine suddenly inoperative with the working engine at maximum rated T/O power in T/O configuration (=gear up)"

Flight controls really work based on a very simple principle:
airflow x deflection= effect
Since airflow is speed it means speed x deflection= effect.
Vmc is an aerodynamic control speed.
So at a speed below Vmc you have no (or insufficient) aerodynamic means to maintain control. So you will end up in the trees upside down.
It doesn't even have to be that dramatic, at very low altitude like 20'-30' you don't need a whole lot of bank to get the wingtip to strike and the aircraft will cartwheel. It doesn't need to roll upside down to end up in a heap.


3. I'm sure Flight Safety has a VFR only course, or if not they should be able to adapt the course they have. Simply swap the IFR training flights for extra VFR.

4. Be tempting to fly it with a very experienced ferry pilot.

[lostpianoplayer]

Thanks for this. I think you're right, about ferrying v crating, and will do it that way. One fella on D&G pointed out the same thing - AND volunteered to help with the ferrying!

Re VMC, I want to be clear about the fact that this is NOT an argument - I just want to learn, so please do consider my question in that context. (I've seen too many Q's on Pprune deteriorate into e-yelling matches, and that's not where I'm coming from - I'm in no way an expert on twin ops, and don't know enough to authoritatively start an argument anyway :) So, my further Q is:

Yes, I understand the definition of VMC. I also understand why trying to continue to fly below VMC is likely to result in some version of the scenarios you've outlined. What I don't understand is why, if you were hair-triggered to cut power on the live engine, as close as humanly possible, as well as applying immediate opposite rudder (aileron?), then wouldn't the removal of the live power remove the roll/yaw immediately, and thus turn it into a common-or-garden engine failure situation? (I know, more speed and intertia than a single, so less survivable, but still much more survivable than going in w/o wings level...) ?

Also, a minor addition - I understand the effect of the after market VG kit, which is fitted to this aircraft, is to reduce VMC to very close to VS. Does that make a difference?

Your thoughts welcomed.

[slatch]

First of all you will find you can not fit a C340 in a container without cutting it up. Main problem is the engine mounts to end of Nacelle is over 8 feet 6 inches so it will not fit in a tall container. Over sized shipping is very costly and would be deck cargo getting into all kinds of corrosion issues. So a ferry flight is in your future.

Get Vortex Generators....they lower the VMC by 11 knots on a C340 to 71 knots....plus you get a 300lb gross weight increase.

Short feild takeoffs at low weights are not an issue. We frequently depart from 1600 foot feilds and rotate in about 800 to 900 feet. Yank it off at 80 knots and then put the nose right down to build speed to 100+. Of course if an engine does fail at or right after rotation be prepared to close both throttles quickly if it starts to roll. VMC demos with gear down and 15% flaps show resonable control until 70 knots. But I do believe it would not be the same under a take off situation.

Now landing in 1600 feet can be an issue. If we are not under 85 knots and are not going to touch down in the first 100 feet we go around. If you are under 85 knots and touch down early you can stop in 1400 feet provided your technique is good and you plant it on with no float. We use a slightly high sink rate, 600-700 ft and try to hit in a three point and push the nose over on touch down. Then max braking when able. Hard not to lock up the brakes until under 40 knots.

Great airplanes, shame what is happening to their values.....

[lostpianoplayer]

Slatch, thanks for this. Yep, I've come to the same conclusion re ferry flights. I'll fly it around the US for a long time first, to be sure of the machine, and spend a year planning it, find a highly experienced person to take with me, then I guess it's the Big Blue for me :)

Thank you very much for the real world info - I appreciate it. I do, in fact, have VGs fitted, so I guess VMC is below VSO. Hopefully my machine will have similar performance to yours. Is yours the 310 hp model?

And whereabouts in CA are you? I'll be over there late this month/early Ma to pick up the 340 in Fresno, and will be flying all round the place, particularly anywhere b/w LA & the Bay Area. You obviously know a bit about real world 340 ops. As a new 340 pilot, I'd love to buy you lunch and pick your brains, if you'd be avail. No offence taken if not - maybe PM me either way?

B2N2, I'm still interested in your response, if you feel like it.

Cheers

[B2N2]

Lostpianoplayer, fantastic screen name by the way.
I know too little about 340's to get involved in the short field discussion.
Engine out scenarios at some point always end up in a very gray area.

A twin is only truly different from a single if you respect it's virtues and vices.
The second engine is only able to do you any good if you stay in a fairly abstract performance envelope.
I am currently in a job where we rotate at Vmc +5, climb at Vyse+5 and we do not allow operations from runways less then ASDR.

Having said that, here is the flip side of the coin. Probably some arguments that you are familiar with.
The engines don't know if you are flying over water. The engines don't know that you are flying at night. The engines don't know that you are attempting a very short field T/O.
Outside the above mentioned envelope you are essentially flying a single since the second engine will not do you any good. But then, most of us have several thousand hours flying in a single. We do not hesitate to fly at night, over water or take-off from a very short field.
So is it unwise to explore the envelope of a twin and operate outside of it?
Not necessarily. There are certain area's of the world where this is done on a daily basis. Alaska, Afrika, remote regions of SE Asia.
Here's a great example:
http://www.youtube.com/watch?v=Mhp0jbTpUGM
You just need to be very aware that if things go pear shaped, the chances of walking away diminish compared to a single.
No only weight and inertia is an issue, a medium sized twin can carry heaps of fuel and what I really dislike about light and medium twins is the awkward entry and exit for the pilot. No door on the pilot's side or you have to work your way through the cabin to get to a door. I have absolutely no statistics to back this up but gut-feeling would tell me that survival rates would go up if some more convenient exits were provided. some of the "bad" examples:

P68 Partenavia, look at the location of the door;
http://www.airplane-pictures.net/images/uploaded-images/2007-11/7954.jpg

Rockwell Aero Commander, pretty much same door location:
http://www.futura-dtp.dk/Flysiden/images/AeroCommander.jpg

One of the better ones, Twin Otter:

http://www.nefsc.noaa.gov/read/protspp/RightWhale/noaa%2057.jpg

[Lifeisgood]

The Cessna 340 is a great plane. With RamVI’s and VG’s the published rotation speed is 91 kts with a climb out of 108 kts to safe altitude. To consider speeds below these is crazy. If an engine pukes on takeoff, forget the catlike reflexes and honed skills, get real. If you don’t value your life maybe you wife, child or passenger does. That 335 horse engine hanging on the right side is producing significant torque and is purpose built to roll you over if you are not prepared. It takes time, maybe four or five seconds to stop the fuel flow and actually stop producing power, not to mention the inertia that 2700 rpm of all that machinery spinning takes to slow down. It takes probably 2 rpm, or .000741 seconds with a busted crank to stop the inop engine. That 335 horsepower on the right wing can lift one hell of a lot of metal in 5 seconds without proper counter forces in an asymmetric engine out scenario.

Regarding runway length, I will not fly mine into anything less that 4,000 ft. Landing in 2,500 ft is no problem; however the engine out on takeoff scenario requires a few more considerations. To accelerate to rotation speed, liftoff, have an engine fail and land safely requires at least 2,700 feet for Sky King to do. So why push it, include a safety margin.

If the mission profile does not fit the 340, look at the Maule or the Caravan or other purpose designed short field aircraft. Don’t buy the 340 because you can get a great deal on one and make believe its got STOL capabilities.

[Harmattan96]

B2N2, long time no see.

You can take the Twotter out of your list, there is a pilot side hatch (on all versions as far as I can remember). Take a quick peak at your last photo, you'll see the hinges just visible.
But from your post I'll take it you like the Aerostar concept, entry and exit are pilot side ONLY; I would hate to be stuck all the way on that back seat.
Gotta love planes build by pilots for pilots!
Take a look: Ted Smith-Aerostar 600 (http://www.airliners.net/photo/Untitled/Ted-Smith-Aerostar/1073297/L/&sok=V0hFUkUgIChhaXJjcmFmdF9nZW5lcmljID0gJ1RlZCBTbWl0aCBBZXJv c3RhcicpICBvcmRlciBieSBwaG90b19pZCBERVND&tbl=photo_info&photo_nr=17&prev_id=1082021&next_id=1049236)

[Big Pistons Forever]

I have about 350 hours flying a VG equiped C340. I think it is the best combination of speed, wx capability, comfort, and economy in its class.... for operations from one IFR airport to another with a max of 4 people. "But" and sorry to be blunt, I think anybody who operates this airplane into a 1600 foot strip needs his head examined.:hmm: Yes it can be done but there would be absolutely no margin on either takeoff or landing.:{ Our SOP was a 3000 foot field as a min and every take off was 0 flap with a 100 knots rotation speed(blueline on a VG machine) with selecton of the gear to up as the decision point (i.e. with gear down both throttles must be closed and you take your lumps straight ahead, with gear coming up takeoff is continued and engine failure handled as an in flight emerg)

Bottom line buy an Islander if you want to go into the really short strips.:ok:

[lostpianoplayer]

Been away or a few days, but yeah, Lifeisgood & BPF, I take your point(s). I haven't, in fact, done ANY flying in a 340, let alone off a short strip. So I'll have to save the head examination till I get the new beast and decide where to base it :) Nor am I here to argue, so, um, I won't! I'm just researching the question, at this stage, and comparing viewpoints. Particularly on the issue of why you can't just cut power immediately to prevent a VMC roll on takeoff.

There are a whole lot of reasons for why I'm asking this, and yes, I hear ya. I guess I wasn't suggesting catlike reflexes, so much as normal reflexes, but being wide awake to the possibilities of emergencies, as opposed to getting complacent. And, like it or not, there ARE differences in pilot abilities, currency and so on, so some minimum field lengths for commercial operators, for instance, have to be a minimium that works across the board. But I hear you guys, loud & clear. Thanks for the input.

[Big Pistons Forever]

One of the problems with training for the multirating is all engine failures are

1) expected, and

2) always total.

Unfortunarely the real world is rarely so accomadating. Many engine problems manifest themselves as engine surges ( can be intially difficult to detect as airplane yaws back and forth) or partial failures ( potentially leading to shutting down an engine producing power ) or prop under or overspeed. While in theory rotation below VMC followed by engine failure can be survived by instantly reducing power on the operating engine, I would suggest that in practice most pilots are going to wind up as a smoking hole in the side of the runway

By the way one of my pet peeves is frequent discussion on this forum about how pilots will evaluate the situation and then use their judgement to decide how to deal with an engine failure during takeoff. Airlines have a defined go no decision point with a set of unvarying actions before and after that point.

This came about after many crashes proved preprogrammed responses to these kind of emergencies was the most effective way to deal with an engine failure during the takeoff sequence. So what makes PPL's think they have more cognitive power to dal with a bad situation, than a 30000 hr airline pilot who will only utilize rote preprogrammed responses :confused:

Thar is why the owner and I adopted the proceedure I outline in my earlier post. It is the closest we could think of to duplicate the airline SOP.:ok:

[SNS3Guppy]

Vmc is an aerodynamic control speed.


No, Vmc is a certification value. The actual aerodynamic control speed varies with a number of factors, ranging from CG to density altitude, flap position, gear position, and gross weight.

A large part of this discussion (which really ought to be centered on the 340, rather than aerodynamics or procedures) has been about the ability or efficacy of preventing a Vmc roll following engine failure while taking off at speeds less than the minimum single engine control speed.

The airplane will not, as a rule, snap roll inverted and crash. Control may be lost faster than you think, however. Regardless, why would you want to find out? It seems the point of the questioning is to see if you can take off at a ridiculously slow speed and still manage to pull back both engines in time to prevent a roll. Rather than do that, how about using a longer runway and flying the airplane at a speed which does maintain control...and flying the airplane instead?

[boguing]

All too true. I've done an engineering type degree and my Pa was an engine designer. When an engine is just about to go t*ts up, it always seems to be running better than ever. Two stroke petrols deliver most power when just so weak they're about to seize. My Land Rover (recent toy) gets really nicely blippy on the throttle when it's about to run out of fuel (must re-time the injector pump).

Never underestimate the power of the buggers to bite you on the arse.

It 'can' be argued that twice the possibilities, four times the problems.

[lostpianoplayer]

...and one of my pet peeves is the argumentative tone that things can take here on Pprune, so, I'm not going to argue. I'm here for education....

Re the parallels between airlines and private flying, I agree to a point, and particularly on the idea of pre-programmed responses to certain events. I try to emulate that approach as much as poss in my own flying. But let's not forget the airlines aim for - and achieve - FAR higher safety levels than we do, at a certain cost. If we were to aim for the same levels of safety, we would only ever fly out of balanced fields, we'd have a fully trained co-pilot on each flight, we'd have turbine engines with ample excess thrust so a serious climb rate is attainable on one engine, we'd have professional flight despatchers, and we'd have....er....an airline :)

But no, I don't maintain I have more cognitive power than experienced airline pilots. Just a much, much wider range of situations to assess, sometimes, and less SOPs. More privileges. More freedom. More risks.

At private level, therefore, we have the privilege of assessing and operating to our own levels of risk. So we don't, in fact, always fly out of balanced fields, we certainly can't climb out on one engine if we're flying a single and the engine quits, etc.

I'm asking about the concept of lifting off slow, and then if the engine fails, pulling the other one and accepting a controlled crash, cos I'm trying to work out whether I could or should operate into my own private strip. I fly a lot of single engine STOL Ops, (on a different field - my one is actually very long for a normal single engine aircraft) and I guess I can't really see the difference between flying off a short field in a single, and accepting that if the engine fails in the first 5-10 seconds after airborne you're in deep trouble, and doing the same in a twin. Double the engine failure risk, of course, but neglible + neglible = close to negligible, doesn't it? I'm guessing that we're talking about a 5 second period between rotation and a reasonable VMC-proof speed. Again, I'm NOT here to argue - I'm here to learn. And nor am I attached to doing so - I'm just trying to figure it out. But that's the context, and the reason I'm asking...

[Lifeisgood]

Listen mate, put a sock in it.

The 340 with RamVI’s and VG’s has a published time from takeoff roll to 100 kts of 15 seconds at GTOW. The time frame from VMC speed to Blueline, which is VYSE (also 100 kts), is about 6 seconds. The most critical timeframe is those magical seconds when you are still earthbound and accelerating through the VMC speed and the wings are starting to fly. The problem is the little bugger wants to fly like a blooming pigeon. Around 75 to 80 kts the wings just come alive like Elton John in front of a grand piano. Your flight instructors have beat into you the need to keep the bird on the ground until the wind going over the rudder reaches at least 91 kts. They did this so that in the event one of the engines craps out there will be enough wind over the tail to give you a bloody chance of surviving the mess. Now if your nose wheel is still on the ground around this time (speeds from 70 kts to 90 kts) you will still have some directional control if you lose an engine. If you pull the nose wheel up to soon, say at 75 kts, and you then lose an engine, it would be arse over elbow mate. You see, the bloody wind would not be strong enough to give your rudder, that’s the tall thing sticking up at the rear of the aeroplane, enough counter force to offset the asymmetric force of a 335 hp engine four foot off your centerline trying to yaw the nose over to that ditch next to the runway. The safest thing to do is stick to the plan, published rotation speeds, balanced field length, plenty of recurrent training and a heavy dose of common sense. If you do all of these things your friends will think you are simply brilliant.

[SNS3Guppy]

But let's not forget the airlines aim for - and achieve - FAR higher safety levels than we do...


Heaven forbid that you seek for,or train to a high level of safety. You don't seek argument, and that's no argument. You have absolutely NO excuse for failing to seek the highest possible level of safety. Moreover, you have every responsibility to do so. That's your job description as PIC, in fact.

But no, I don't maintain I have more cognitive power than experienced airline pilots. Just a much, much wider range of situations to assess, sometimes, and less SOPs. More privileges. More freedom. More risks.


As a private pilot you hold more privilege than the holder of an ATP? Really?

No doubt from your questions and comments you take more risks. That's nothing of which to be proud.

I'm asking about the concept of lifting off slow, and then if the engine fails, pulling the other one and accepting a controlled crash, cos I'm trying to work out whether I could or should operate into my own private strip.


You're asking the wrong question.

The real question should be what length runway you need to depart in order to achieve adequate takeoff speed and distance to enable safely handling the situation if an engine quits. If you're asking if you can handle one quitting while attempting to climb out or takeoff below Vmc, you're asking a stupid question. There really is such a thing as a stupid question. What you're really asking is "If I do something stupid, what are the chances that I'll be fast enough to save myself from my own stupidity?" Which of your instructors taught you to take off below Vmc?

Not that it's not possible to do by any means...but certainly the inexperience offered in the way you ask and your tone suggests that it's not something for you. Of course, you also sound like you intend to do as you please, without regard to what others may have to say.

But let's not forget the airlines aim for - and achieve - FAR higher safety levels than we do, at a certain cost. If we were to aim for the same levels of safety, we would only ever fly out of balanced fields, we'd have a fully trained co-pilot on each flight, we'd have turbine engines with ample excess thrust so a serious climb rate is attainable on one engine, we'd have professional flight despatchers, and we'd have....er....an airline


What makes you think an airline must operate with a balanced field? A balanced field is one in which the accelerate go distance equals the accelerated stop distance, and this is very seldom the case. Rather, a rejection speed is computed which establishes a maximum speed to which the flight can accelerate before recognizing the problem and rejecting the takeoff. If the resulting stopping distance approximates the required takeoff distance, it's merely a coincidence.

You shouldn't be taking off, however, unless you have the ability to recognize the problem, and reject, and stop in the remaining runway, or stopway.

The issue of a first officer is largely one of aircraft certification and the regulations under which the flight is conducted. There's no question that in a highly complex, advanced aircraft, a SIC can be not only necessary, but immensely helpful. However, you make a poor comparison. Your aztec vs. a B747, for example. Consider also the complexity of operations, and the kindof flying you do may not require it. This does NOT mean you are excused from operating at the highest level of safety, and maintaining the highest level of proficiency. You have that full responsibility; operating privately does NOT excuse you from that.

Flight dispatchers are an operational requirement, and not all airlines use dispatchers. Some use flight followers, and not all of them are professionals. You, however, have the same responsibility in full to calculate your performance, know your fuel, your weather, your distances, your climb rates, and your capabilities before you go. Don't try to excuse yourself to a lesser level of safety merely because someone else isn't making the calculations for you. Moreover, regardless of who makes the calculations, the PIC is always responsible for them.

You don't need a turbine engine to act safely. Nor do you need it to assess takeoff performance or plan for it.

You could do that sub-Vmc takeoff in a turbine powered airplane and achieve the same results...if you're below Vmc, it won't matter if it's turbine or piston...pushing the power up will only aggravate your problem, and the fact is that your problems at that point are only compounded. So again, your comment really has no relevance to the conversation here, nor is it an excuse for acting unsafely.

I get the distinct impression that no matter how many people tell you not to go jumping into a higher performance airplane with a little more complexity, and taking it off Vmc, you're going to keep on asking until someone tells you it's okay. Anyone who doesn't is being "argumentative."

I guess I can't really see the difference between flying off a short field in a single, and accepting that if the engine fails in the first 5-10 seconds after airborne you're in deep trouble, and doing the same in a twin.


Therein lies the problem. You're already flying an aztec, you said. You shouldn't have to ask this question.

You're in deep trouble only if you fail to plan accordingly in the single. Your takeoff should be planned such that you already know where you're going to go and what you're going to do. You're going to be landing at a slower pace with far less mass energy, with a much lower stall speed, much lower touchdown speed, and better slow speed landing characteristics in the single; you can glide much more comfortably, farther, longer, and have none of the inherent dangerous characteristics that take place in the twin.

You may have no choice but to retard the good engine when a failure occurs in a light twin. It happens. However, especially in an airplane such as the 340, you should be planning your takeoff such that your weight, takeoff distance, and obstacle clearance area and departure area mean you don't have to. If you plan your takeoff by intentionally departing from such a short strip that you have zero options and your game plan is to put yourself in an emergency situation below the minimum control speed, then you've already decided to live a mistake before you ever start the engine. Starting with the fact that you've already placed yourself in a position where control may not even be possible.

Add to that the fact that aircrat such as the 310 and 340 use tip tanks with additional mass in the tip tanks and once a roll starts you may not be able to stop it.

Double the engine failure risk, of course, but neglible + neglible = close to negligible, doesn't it?


There again is a big part of your problem. You're assuming, guessing. Your condemn the airline operation for it's high level of safety, which is a foolishly mind-blowing concept in it's own rite. However, safety need not be the purview of the airline pilot alone, nor the corporate pilot only...it needs to be yours. The difference between you and the professional pilot is that the professional pilot plans the takeoff with a failure in mind, not hoping that it doesn't. Forget professional...the responsible pilot plans in advance for each contingency, and thus plans for the safe outcome of the takeoff regardless of whether the engine fails or not. You don't need to be flying a transport category airplane to do that.

And to answer your question, negligible doesn't equal negligible. Your engine will either run, or it will not; that's a one out of two chance, and it doesn't get any better the longer you fly...or the more engines you carry. You have that opportunity every single takeoff, and had better be planning for it. Not just assuming it's such a slight risk it probably won't happen. When it does, in the twin you not only lose 80% of your available thrust, but the remaining value is fighting to take control away from you.

Strive to eliminate risk, not embrace it.

I'm guessing that we're talking about a 5 second period between rotation and a reasonable VMC-proof speed.


The problem is that unlike having a failure occur at a speed above Vmc where you have the luxury of losing airspeed all the way to the minimum control speed...when you lose the engine below Vmc, you can't accelerate to Vmc. Adding more power only aggravates the problem. That leaves you in a regime where your ONLY choice is to reduce power on the good engine because you have no more aerodynamic control authority. Often this speed occurs close to the stall speed, which will also be the case if you're attempting to depart from a very short field near minimum control speed...and you can get there in a big hurry as you slow when the first engine goes. You have to recognize and react to the situation (an inexperienced pilot will invariably attempt to push the power up, rather than retard it, and handle the directional control with aerodynamic controls alone), and then correctly apply reduction of power on the good engine.

In the meantime, you're applying opposite rudder to the failed engine, and opposite aileron. You're already slow, at a high angle of attack, and at maximum takeoff power. The lowered aileron on the side of the bad engine increases the local angle of attack, increases adverse yaw, increasing the effects of the failed engine, as well as potentially causing a stall along the section of wing occupied by the aileron. The yaw is made worse, the roll is made worse. As the wing starts down in the 340, additional rotational inertia is imparted to the fuel in the tip tanks, making the turn and the roll even harder to stop. Additionally, as the wing with the good engine still has airflow, local lift is created which isn't available on the side with the bad engine, increasing the roll. Further, as the yaw occurs, the wing with the good engine moves forward increasing lift, while the airflow over the retreating wing decreases lift, further aggravating the roll. Even if you pull the power, you may continue to roll once it's started. How far, how fast, really depends on some of the factors previously cited (including CG, flap position, gear position, weight, density altitude, etc. If you're near the ground at the time, you may not have to roll very far before you catch a wingtip, and you may be lacking the performance to climb much to avoid it. Your time to recover is further reduced.

Rather than find out when it's too late, don't put yourself in that position to begin with. You needn't be an airline pilot to be safe.

[lostpianoplayer]

OK. Enough things being taken out of context here to see this discussion isn't going anwhere. If it seriously seems as though I was "condemning" the safety culture of the airlines, or not trying to minimise risk myself, I guess I need to work on my writing skills -or qualify everything I say with so many modifiers & caveats that the meaning gets lost. But this isn't a legal thesis we're writing, it is, or was, an educational discussion, for me anyway. Ain't the anonymity of the internet wonderful? You can argue amongst yourselves. I'll think seriously about the issues raised in the thread though, and thanks to all, particularly the earlier posters who said what they had to say without the testosterone haze getting in the way. Sock duly placed. Seeya.

[SNS3Guppy]

OK. Enough things being taken out of context here to see this discussion isn't going anwhere... You can argue amongst yourselves... Seeya.


That's pretty much what I figured you'd say.

So far as out of context...you were quoted. Not taken out of context.

[B2N2]

Some of you need to relax a little behind that keyboard.
...insert arrogance......
Not everybody is as experienced as "we" are.
...turn off arrogance...

There is no such thing as a stupid question, but there is such a thing as a stupid answer.
Why don't we simply try to answer and educate?

[Lifeisgood]

To SNS3GUPPY, very well said!

To B2N2, no arrogance intended, just concern that some soul was not listening to good advice. Line one of his post referred to looking for advice.

To Lostpianoplayer, flying a light twin like a 340 is a joy, please keep safety number one.

I for one enjoyed the exchange; conflict hones the skills and allows everyone to reassess their values and opinions. As pilots it is these values and opinions that dictate our actions, or lack of actions. If we do not express disapproval of an unsafe procedure, what kind of pilots are we?

[bookworm]

In a twin rotation speed should not be below Vmc

A large part of this discussion (which really ought to be centered on the 340, rather than aerodynamics or procedures) has been about the ability or efficacy of preventing a Vmc roll following engine failure while taking off at speeds less than the minimum single engine control speed. (my bold)

Can you guys who assert this explain in terms of the aerodynamics why you believe a catastrophic engine failure at Vmc - 5 knots leads to more significant control problems in the air than on the ground, please?

[411A]

Can you guys who assert this explain in terms of the aerodynamics why you believe a catastrophic engine failure at Vmc - 5 knots leads to more significant control problems in the air than on the ground, please?

Because...while still on the ground (nosewheel especially), more directional control is most times obtained (due to said nosewheel)...however, with many light twins, you might end up in that ditch off to the side of the runway anyway, unless you are jolly quick, and have quite good skills.
Even if throttles are closed, going off the end OR ending off to the side, is far better than finding oneself rolling inverted...with most times deadly results.

[bookworm]

Because...while still on the ground (nosewheel especially), more directional control is most times obtained (due to said nosewheel)...

I'm not sure that directional control is guaranteed. Let's ask the Q on Tech Log where the certification folks hang out.

[411A]

I'm not sure that directional control is guaranteed.

Ahhh, bookworm, you might read again what I stated originally.
Didn't say anything about 'guaranteed'.
And, I answered your question in Tech Log, with regard to 14CFR23 aeroplanes.

[Lifeisgood]

Nothing is life is guaranteed, but proper training and understanding of Vso, Vmc, Vyse, accelerate-stop charts and other asymmetric forces are very important to safely fly a multi-engine aircraft. The pilots whom have taken time and responded to these questions have succinctly stated that Vmc is a critical factor in flight safety considerations. I have no dog in this hunt. However the author of this rant suggested taking a course at Flight Safety, I think the Kansas location handles the 340 training and you could not ask for a better solution to this question. The instructors at Flight Safety are very professional and have the ability to demonstrate in a simulator various scenarios. I wish I could be there to observe what will happen if someone attempts rotation at 70 kts and with gear down and has an engine fail. If you do this, please send me an email and let me get some friends together with a cooler of Bud Light, I’ve got a friend at F/S and I think we could observe. I suspect it would take about 5 seconds until either a cartwheel occurs or the AI is brown over blue. I am sure the trainers will be amused; they have a passion to “educate” us. Simulator training is a wonderful way to envisage in a secure environment what realities could occur in real world situations. One of my personal favorites is losing an engine in hard IFR, 600 ft ceilings, 30,000 ft tops, no GNS530 or GPS on board, 30 nm from destination and then have your remaining alternator fail. If you’ve never sweated in a 65 degree cockpit you will in the Sims. If the author does follow through with the Flight Safety training he might consider doing a Youtube video to publish this takeoff scenario for others to benefit from.

The simplest and best answer is get proper training.

I'm out of here.

Life is Good

[bookworm]

Ahhh, bookworm, you might read again what I stated originally.
Didn't say anything about 'guaranteed'.

And it wasn't my intention to contradict you in that, 411A. In essence, if you're saying that an engine failure at a critical time in the take-off can leave a 14CFR23 aeroplane "in the weeds" regardless of whether it's on the ground or in the air when the failure occurs, then I'd agree.

What I'm arguing is that, if that's true, there's no point in being precious about whether you rotate above or below Vmca. The decision is simple: if an engine failure occurs below Vmca, you close the throttles and do the best job you can, whether you're on the ground or in the air.

[SNS3Guppy]

Bookworm, you really confuse the issue by taking it between multiple threads or forums. For others following along, the reference question in Tech Log is http://www.pprune.org/forums/showthread.php?t=326493&highlight=Vmcg

You also are asking about different subject. In the tech log question, you asked about Vmcg, which is not the same as Vmca. One is minimum ground control speed, one is minimum control speed in the air; each have different criteria and requirements.

When 411a says that a part 23 airplane doesn't have gauranteed performance after takeoff, he's correct. This isn't at all the same thing as a Part 25 airplane, which does have certain performance "gaurantees" based on the nature of certification. For example, a multi engine airplane certificated under Part 23 isn't required to maintain altitiude after an engine failure, by virtue of it's certification, nor is it required to be able to go around on one engine, fly a missed approach with an engine failure, etc. Part 25 certificated aircraft are required to meet specific climb gradients following loss of an engine on takeoff (which translates to a go-around or missed approach, too). The Part 25 airplane has certain performance "gaurantees," whereas the Part 23 airplane does not.

You're getting confused between topics, when asking about Vmcg and Vmca.

An engine failure on the ground which occurs below Vmcg means that unless corrective action is taken, directional control of the aircraft is not possible. Full aerodynamic application of rudder will not correct for the loss of directional control. The loss will occur as lateral deviation from the centerline, or in other words, the aircraft takes off in a different direction. Vmcg calculation does not take into account the effects of nosewheel steering or differential braking. Vmcg is less than Vmca, and if during a takeoff a failure occurs prior to Vmcg, clearly one's option is to reject the takeoff, because directional control is no longer possible.

Vmca is another matter. The airplane doesn't simply turn left or right. For reasons previously provided in this thread, a rolling motion is imparted, and for reasons already given in this thread that rolling motion may not be stoppable or preventable...even if the power is pulled back. Particularly in an airplane such as the 340 where the tip tanks tend to exacerbate the problem of stopping any rolling motion once it's started, and particularly at low airspeeds when control authority is less. Particularly at low airspeeds when control authority is less, when one has elected to take off at speeds less than the minimum control speed. I think you see where that's headed.

On the ground, you may end up in the weeds if you don't act properly. In flight, you may end up in the weeds, upside down, on fire. You see the difference, perhaps.

So, you ask, what's the big deal taking off below single engine minimum control speed if you might have directional control problems before or after taking off?

Consider the alterantive, when acting prudently. One takes off at an airspeed which permits safe control of the airplane in the event of an engine failure. One is above Vmc, and has the luxury still maintaining control with appliation of rudder, banking into the good engine retracting flaps and gear, and climbing (where possible) at Vyse. When losing an engine after takeoff when below Vmca, one is gambling, and has no chance of climbing out. If one is very close to the stall speed, which is very possible, one may experience a very rapid loss of control with no chance of stopping the event. Add to that the fact that your first inclination in the event of an engine failure is to push the power up...not pull it back. This only makes things worse.

By taking off at a speed which permits full control, you have options. You also have time to act and react, configure, prepare for either a forced landing or a climb out at Vxse or Vyse, and to handle the problem. In other words, you're prepared.

Sad experience over many decades of multi engine training, testing, and flying has taught the industry these things. The FAA, for example, stopped allowing even engine failures on practical tests at any more than 40% of the takeoff speed, due to the number of accidents during practical tests for pilot certification, when performing a high speed rejected takeoff. That's even before the aircraft gets off the ground, when a loss of directional control is far less critical. Loss of directional control in the air, especially on takeoff, is about as critical as you can get.

A light twin may or may not be able to climb out on one engine. Whether it can or not, even if it's just holding altitude or maintaining control, it's far better than actually intentionally planning for a takeoff when there's no such possibility whatsoever.

The 340, depending on weight and density altitude, is capable of climbing (at a very reduced rate) on one engine. If one has planned one's takeoff properly, having remained on the ground until above Vmcg and taking off above Vmca, the option and ability is then available to clean up and fly off under control.

For airplanes which will not maintain altitude on one engine, one still has directional control in one's favor if one has properly elected to fly above Vmca, and one has a significantly improved ability to put the airplane on the ground under control, at a controlled rate of descent...as opposed to the original poster's plan of simply intending to yank the power back on the good engine and accept whatever lies beyond.

I don't know if the original poster has had occasion to arrive at an altitude of 30' or so above the runway on takeoff and suddenly retard power on one engine, then the other, and attempt to reach the ground...he doesn't appear to have had the experience of a real engine failure at all. Certainly not with one engine having failed while below Vmc, then while starting to yaw and subsequently roll (again, for reasons already explained in this thread), attempt to pull back the other engine and then land the aircraft...but you may rest assured that he doesn't want that experience. Nobody does. Even without the loss of control, attempting to suddenly lose power and then get that airplane to the ground is not at all the same as losing one's only engine in a single, and gliding. In fact, he's got a high probability of stalling it in the process. As well as doing it while yawing and rolling.

Think about it.

[Lifeisgood]

Bloody Hell but you gave him a thrashing. He’s no doubt in the bottom of his foxhole right now tending to his welts.

For God, Country and the Funny Acronym Association

[Lifeisgood]

At first I was worried that someone might actually be listening to what you are suggesting. Then I realized you are simply being argumentive, and that’s OK. I will also have faith that anyone that has a ME rating probably has a MEI and therefore has been trained by competent and knowledgeable CFI’s that teach solid aerodynamics principles (pardon the pun), safety practices and smart piloting techniques.

To that end I say, ask all the dim questions you want, assail us with foolish theories on rotation before Vmc, go ahead and run biofuel in you avgas engine.

In the words of Monty Python “I don't wanna talk to you no more, you empty headed animal food trough wiper! I fart in your general direction! You mother was a hamster and your father smelt of elderberries!”

[SNS3Guppy]

People should quote Python more often, lest we be blindsided by an exploding Scot, or attacked with fresh fruit,.

[bookworm]

SNS3Guppy

In amongst what is undoubtedly good and thorough explanation, and also some rather patronising comments about what you think confuses me, is the central issue, which you put quite concisely.

On the ground, you may end up in the weeds if you don't act properly. In flight, you may end up in the weeds, upside down, on fire. You see the difference, perhaps.

The question, which I don't think you've answered yet, is why you think that on the ground you don't also end up "upside down and on fire". If the aerodynamic forces after an engine failure at that particular speed will roll the aircraft after its wheels have left the ground, why do you think that you will be spared if the wheels are still on the runway?

One possibility, put by 411A, is that the nosewheel offers a lateral force opposing the yaw and gives you a better chance of keeping the nose in front of the tail. But as I think we've now examined on Tech Log, no one seems to be able to come up with a certification requirement that suggests that the lateral force from the nosewheel will be available and sufficient to do so, even for a subpart 25 aircraft.

The Part 25 airplane has certain performance "guarantees," whereas the Part 23 airplane does not.

And that again, is pivotal. Once a subpart 25 aircraft has reached V1, which must be at least Vmca, there is that certification requirement that the aircraft can continue the takeoff. And because we rotate at or above V1, it's obvious that for such an aircraft we would never take it into the air below Vmca.

For a subpart 23 aircraft, the situation is different. Even after we take the aircraft into the air, we know that in the event of an engine failure we may simply have to do what we would do on the ground -- close both throttles and do the best job we can to keep it straight. If we fail to do that below Vmca, then of course we will "end up in the weeds, upside down, on fire". Even if we fail to do that above Vmca, there is a good chance we're still going to end up in the weeds and on fire because we don't have the performance to continue flight. Only when we reach a speed at which we know we can climb away on one engine (and I would choose Vyse) can we change the instinctive reaction to an engine failure and attempt to keep flying. Below that speed at which we would commit to flight, we close the throttles.

So for a subpart 23 aircraft, Vmca is not a useful speed at which to make that decision to commit to flight. It's usually way too low. Is it a useful speed to choose as a minimum for taking the aircraft into the air? Well the only reason it would be might be that there's a speed range below Vmca within which the aircraft is controllable on the ground but not in the air. And I'm waiting for you to explain why such a speed range should exist.

[SNS3Guppy]

The question, which I don't think you've answered yet, is why you think that on the ground you don't also end up "upside down and on fire".


Actually, I did answer that, and hopefully this won't be too patronizing for you; READ!

An aircraft rolling along the ground doesn't mystically flip upside down, but an aircraft rolling out of control just after takeoff has no problem. You do see the difference, don't you?

If the aerodynamic forces after an engine failure at that particular speed will roll the aircraft after its wheels have left the ground, why do you think that you will be spared if the wheels are still on the runway?


Yes, on the ground, the ground is in the way. The hard surface under you. That ground. In flight, it's not in the way. One wing dropping on the ground in order to effect a roll isn't nearly the issue it might be in the air, owing to the wheel being on the ground, you see.

One possibility, put by 411A, is that the nosewheel offers a lateral force opposing the yaw and gives you a better chance of keeping the nose in front of the tail. But as I think we've now examined on Tech Log, no one seems to be able to come up with a certification requirement that suggests that the lateral force from the nosewheel will be available and sufficient to do so, even for a subpart 25 aircraft.


That is because Part 25 does not permit considering nosewheel steering or differential braking in establishing Vmcg. You're going to really confuse yourself when you get into Part 25...especially where we're talking light aircraft certificated under CAR 3 or Part 23. You appear somewhat confused between Vmc and Vmcg, as well as the various certification regulations. No one came up with a reason because there isn't one...it's not used. The stabilizing influence of the nosewheel must be considered negligible, and therefore irrelevant, in establishing Vmcg.

Even if we fail to do that above Vmca, there is a good chance we're still going to end up in the weeds and on fire because we don't have the performance to continue flight.


You may well end up in the weeds, but perhaps you've forgotten the most basic requirement of flying the airplane: fly the airplane. Your best outcome occurs when you're still in control. Whether you must still land is really quite irrelevant. Whether you do it under control is very relevant. Again, I'm sure you can tell the difference.

Only when we reach a speed at which we know we can climb away on one engine (and I would choose Vyse) can we change the instinctive reaction to an engine failure and attempt to keep flying.


You may never be able to climb away on one engine, depending on the airplane and your available performance. That's something you need to have planned for and calculated before you ever elect to undertake the flight. Know before you go.

Below that speed at which we would commit to flight, we close the throttles.


That flight will be your refusal speed, sometimes denoted as such, sometimes referred to as decision speed, V1, or in some cases, simply rotation speed. In any event, per the topic of this thread, it needs to be above Vmca, which is really the whole point.

You need to bear in mind that Vmcg is a technical number, as is Vmc. These are certification values. In a light normally aspirated piston twin, Vmc decreases with an increase in density altitude, and decreases in many cases with gear down, with the addition of flaps (though not necessarily), with a forward CG, etc. A published Vmc number does not necessarily represent the number at which directional control is no longer possible. The number may be less, and in some cases, it may also be more. It's a reference number. The same may be said of Vmcg.

Vmcg, for example, is one number; a certification number. The speed at which directional control may no longer be maintained does change; it can be increased at a rate roughly on a ratio of one to one with a crosswind, increasing one knot for each knot of crosswind on the side of the failed engine, and decreases at roughly the same amount for a crosswind from the other side. Other factors may also affect the minimum controllable speed, most notably among them the center of gravity.

And I'm waiting for you to explain why such a speed range should exist.


You ask why a difference should exist between Vmcg and Vmca, is that it? You want to know why there's a difference between stall speeds clean and dirty? Why some airplanes are monoplanes, some biplanes, some triplanes? Why there's a difference between fast and slow? Or was that just a rhetorical question?

Vmcg occurs typically at a lesser speed than Vmc, but not always; the two may be coincident. Flight speeds are typically greater than ground speeds, as you can guess. The range does not exist between the two because it has a purpose; it does not. It exists because it exists. However, even though one has obtained Vmcg does not mean one is ready to fly, and accordingly one must be above Vmc prior to taking the airplane into the air.

Perhaps you meant something else.

[lostpianoplayer]

Bookworm, I've been following this thread since leaving these two people to their fun, cos I find the name-calling, patronising assumptions and so on to be a bit dull. I mean, I already went to high school, you know? But I thought their might some pearls of wisdom to be salvaged, or wheat amongst the chaff. (Choose your metaphor :) And there are.

To your specific question re VMCA vs VMCG: "If the aerodynamic forces after an engine failure at that particular speed will roll the aircraft after its wheels have left the ground, why do you think that you will be spared if the wheels are still on the runway? "...well, I wonder if there may be a pretty simple explanation.

It seems to me that you'd much less likely to roll if you're still on the ground, with a high speed engine failure that occurs before rotation, primarily because the "wheels on the runway" act as a stabilising factor against the development of a roll, or to be precise, the wheel that is under the failed engine, and therefore holding up that wing to some degree. Sure, you'll yaw, although nosewheel steering & differential braking may control that to some degree as you retard the working engine...but when on the ground, you have the the main gear to at least partially oppose a rolling motion, no? When practicing high speed engine failures, yes, with a very experienced instructor, I recall a startlingly fast yaw, until the good engine was retarded - but no hint of a roll. And even if a roll did occur and overpower the stability of having wheels on the ground, if you're still on the ground you have a wingtip to hit the ground first, which means that it could be ugly - but probably not as ugly as ending up completely inverted when airborne, where you'll presumably have a serious ROD, even from 20 feet or so, to compound the problem. So the most likely worst case, I would guess, would be departing from the runway - but right side up, and rapidly regaining yaw control as the power from the working engine winds down. Provided you cut power immediately, of course.

Once you're in the air, you've got no wheel on the ground under the failed engine to act as a stabilizing factor, and oppose the rolling motion, so a roll, it seems to me, would be far more likely to occur. And once the roll gets going, it could indeed, perhaps, be difficult to stop given the minimal effectiveness of controls at that speed.

Could it be that simple? The fact that the standard T/O technique is to holding a twin on the ground until VMC or faster would imply so, dontcha reckon?

[bookworm]

It seems to me that you'd much less likely to roll if you're still on the ground, with a high speed engine failure that occurs before rotation, primarily because the "wheels on the runway" act as a stabilising factor against the development of a roll, or to be precise, the wheel that is under the failed engine, and therefore holding up that wing to some degree.

...Could it be that simple?

It certainly might help, depending on how much lift you're getting before rotation. With all the weight on the wheels and no lift, there will be no asymmetric lift and therefore no rolling moment. Once all the weight is off the wheels, the lift is as it is during flight and the aircraft will simply roll into the dead engine. The wheel won't stop the roll, nor will the wingtip. If you're achieving partial lift before rotation, the effect will be somewhere between.

The fact that the standard T/O technique is to holding a twin on the ground until VMC or faster would imply so, dontcha reckon?

There are many "standard techniques" in aviation that rely on false assumptions or make simplifications that are suitable in one case but not in another.

The aircraft I fly develops considerable lift in its recommended take-off configuration well below Vmca. At Vmca, if I hold it on, I'm holding it on the nosewheel, with no weight on the mains. An engine failure at that stage would be more catastrophic on the ground than in the air (where I could use some bank to assist control). The AFM simply says "keep it on or close to the ground until take-off safety speed".

If an aircraft can be kept on the runway producing little or no lift, and then rotated into a flying attitude, I can see an advantage in staying on the runway until Vmca. Perhaps that's the case for the 340. But I'm not convinced by the general case.

[SNS3Guppy]

Why not simply use the standard procedures provided by the manufacturer, including the rotation speed provided in the performance charts? How difficult is that?

[Big Pistons Forever]

I think the VG equiped C340 is one of the safest piston twins when it comes to a takeoff engine failure emergency. That is because you can rotate at the 100 knot blueline VYSE speed. If the the oleos are properly inflated the airplane will sit level and therefore not want to fly untill it is positively rotated (this only applies with zero flap). Therefore if you select gear up immediately after rotation (as soon as you have positive rate of climb, of course) you will only have to feather the failed engine and the airplane will be at or above blue line and configured to climb away (i.e. flaps will allready be up and the gear will be retracting/retracted). Our SOP is to keep our right hand on the throttles untill selecting gear up and then move our hand to the prop levers. therefore if an engine failure happens with hands still on the throttles we would automatically retard both throttles and reject the takeoff. If the engine failure occures with our hand on the prop levers we would identify he failed engine (dead foot, dead engine) feather it and concentrate on keeping the airplane straight and set an initial 5 deg nose up attitude then adjust to maintain VYSE. We felt this procedure allowed us to come closest to a large aircraft SOP and therefore their levels of safety.

[bookworm]

lostpianoplayer, after a digression into controllability, may I return to what I was going to say before SNS3Guppy and I locked horns (though how a fish and a worm lock horns is beyond me ;))?

I'm just researching the question, at this stage, and comparing viewpoints. Particularly on the issue of why you can't just cut power immediately to prevent a VMC roll on takeoff.

The problem, in the context of operating off short fields that require lift off at low speed is this. In the ideal world, engine failures are infrequent and sudden. You recognise the failure, chop the throttles, go through the hedge at the end and accept that the insurance company owns the aircraft.

Real life is less straightforward. You accelerate beyond the speed and runway point at which a safe rejection is possible, but still below Vmca, and the engine coughs -- I could equally propose an oil pressure gauge in the red, or a strange noise from one engine. You now have a choice. You can leave the throttles where they are, continue to try to fly it, and risk a sub-Vmc roll. Or you can close the throttles, go through the hedge and accept the hull loss for sure. It was probably just a little cough, right? How lucky do you feel?

Coughing engines, sticky oil pressure gauages and unfamiliar noises are, fortunately or unfortunately, a lot more common than catastrophic and sudden engine failure. So unless you feel lucky on a regular basis, the price of operating from a short field is a much higher probability of a precautionary abort and consequential hull loss.

[Dream Land]

Buy a C210. :ok:

[Big Pistons Forever]

Or better still a Roberston STOL C206

[Lifeisgood]

Here is how I takeoff in my 340A, in brief form and I welcome any comments or suggestions;


All pre-takeoff checklists performed.
This includes accelerate stop distance, which is approximately 3,000 ft by the book; however I prefer a 4,000 ft minimum runway length.
Obtain clearances as required.
Lineup on runway, brakes on and increase power evenly to 30 inches MP for three seconds (recommended by Ram Aircraft) and then apply full power while releasing brakes.
Check for engines gauges in the Green.
Call our VMC speed, 74 kts.
Call out Rotation Speed, 91 kts and Rotate, one may also rotate at Rotation minus five knots, but I prefer the higher speed. This is due to wanting to avoid as much as possible any Vmc issues.
My right hand is on the throttles at max power.
Depending on weight, CG and DA, actual rotation occurs in low 90’s
Takeoff occurs and climbout to Vyse, 100 kts. This takes about three seconds from Rotation.
If anything coughs, pukes, thumps or rattles during this phase of takeoff, I will immediately retard the throttles and land straight ahead.
Now is decision time. By selecting gear up with my right hand, I am committing to continue the takeoff. I keep my right hand on the gear lever until I see three green lights and I do not put my right hand back on the throttles.
Accelerate to Vy, 108kts and climbout straight ahead or as directed by ATC to 1000 ft AGL minimum at full power.
During the initial climbout to 1.000 ft AGL I gradually nose over at the top of the climb profile to approximately 140 kts and reduce power to 32 in MP, 2500 RPM and 1500 EGT, a quick engine scan, and proceed with departure as planned.

I believe this is the best method to pilot a 340A on takeoff. Advantages are;


You have adequate runway for a rejected takeoff.
You accelerate through the Vmc speed before Rotation so that Vmc risk is minimized.
You immediately accelerate to Vyse and then select “Gear Up” as THE decision making moment to commit to the climbout, regardless of engine failure, and treat an engine failure as an in flight emergency.
At decision speed you are at Vyse 100 kts, and then accelerate to Vyse plus 8 kts. In case of engine failure and the ensuing long moments to identify, verify and feather, a small loss in speed will result in the target speed of Vyse.
I rarely fly at MGTOW and find the SE climb performance to be 500 fpm or better at GTOW minus 400 lbs.

[bookworm]

I believe this is the best method to pilot a 340A on takeoff. Advantages are;

* You have adequate runway for a rejected takeoff.
...
* You immediately accelerate to Vyse and then select gear up as THE decision making moment to commit to the climbout, regardless of engine failure, and treat an engine failure as an in flight emergency.

Interesting -- and very similar to what we do in the Twin Comanche (Vyse 90 kt). How much runway do you need accelerate to 100 kt and then stop? Wouldn't the published accelerate-stop distance be for 91 kt?

[Lifeisgood]

The takeoff roll, depending on GTOW, DA and temperature is about 1,400 ft. The accelerate stop is about 2,700 ft., according to the book. I have landed and departed in runways as short as 2,700 ft, never again. I admit to being spoiled at my local airport SUS to have a very well maintained 7,500 ft runway that I now accept as “normal”.

[lostpianoplayer]

Hi Bookworm.Yep, I take your point, about rejecting takeoffs in twins for minor engine problems. I'm coming to this issue with a fair amount of experience in short field ops in singles, and also maybe 400 hours in piston helicopters, but not a great deal of M/E time, of which I probably only have 150 hours or so. I did train comprehensively for my M/E rating with a very experienced instructor, have read a lot on the subject, and found my flight test to be quite demanding and comprehensive. I appreciate you taking the time to discuss the issue rationally, rather than rushing into ad hominem attacks cos I’m supposedly asking “stupid questions”. I originally decided to stay out of this issue once the shouting started, but perhaps one more post would be pertinent, particularly since you've added some thoughts that are of value. Thank you.

In both the single STOL situation, and taking off in a piston helictoper - or for that matter flying over, say, forests, in either, one is frequently in situations where an engine failure at an inopportune moment could cost you very dearly indeed. The scenario you paint, in terms of a STOL takeoff in a twin, doesn't seem entirely dissimilar, to me, than that of taking off in a single – EXCEPT for the VMC issue. Once you're committed to a STOL takeoff, or a helicopter takeoff on the not unheard of occasions where you can’t stay within the H/V curve, if you have a 'non-immediate failure' engine burp/twitch/whatever, then you're potentially in a world of hurt. In a single, you have a millisecond to decide between the rock and the hard place, and you're certainly not operating on a balanced field. So the real question, it seems to me, is back where we started – does retarding the power on the good engine prevent a VMC roll or not? It would appear the consensus on the answer is no – a VMC roll, or serious loss of directional control, is inevitable, EVEN IF you immediately retarded the power on the good engine. Well, to those who’ve adoped that position, fair enough. I hear ya. I won’t take off below VMC. I was never intending to. It would have been nice to understand exactly why not, rather than take it at face value, and there are one or two answers here that make a strong case in terms of explaining WHY you can’t retard power on the good engine in time. I’ll think more about this issue, and keep picking the brains of those more experience than me. But, just so you know, I ran this by a 30-years-flying M/E guy yesterday, and guess what? He reckons directional control is quite achieveable, provided you cut power on the good engine immediately. I guess that makes him stupid too? Maybe we’re ALL stupid down here in New Zealand. Or maybe the coriolis effect changes the aerodynamics J

Most pilots spend a great deal of time planning & training for engine failures, either partial or total - but my understanding is that statistically speaking, avoidable engine failures - ie not produced by fuel starvation or mismanagement - are extremely rare, which is why some people choose to accept the risks involved in single engine STOL ops, or piston helis. (And, for the record, I HAVE in fact had 2 engine failures, in 12 years of flying, one arguably my fault to some degree, one unavoidable, so I don't believe they're impossible. Just very uncommon.) In terms of this particular issue, I'd have to stand my my initial comment, whatever the angry poster guy thinks of my training, approach to risk, suitability to hold an M/E rating, or whatever. I STILL "can't really see the difference between flying off a short field in a single, and accepting that if the engine fails in the first 5-10 seconds after airborne you're in deep trouble, and doing the same in a twin", EXCEPT insofar as it is affected by VMC. (And no, angry poster guy, save your aggression & go & kick your dog or something - you've made it pretty clear you're here to preach not to listen).

I'm sorry if I appear stupid to the more experienced people here, but I'm used to the concept of relying on my engine, and to minimising as much as possible but never eliminating the risk entirely, if that engine decides to quit. This is why I've been trying to work out if a VMC roll is inevitable if you rotate at a slow speed, by which I don't mean, necessarily, BELOW VMC - but possibly 5 knots or so below the published rotation speed. Or 10 knots, even. My personal opinion is that factory charts are helpful guides but NOT the singular, authoritative and definitive performance indicators that we would like them to be, so I like to augment the published data with actual date, by checking the actual aircraft's real world performance against the charts. The aircraft may or may not be in "as new" condition, for instance, it may be operating off fields that are neither flat concrete nor "firm sod - add 7%" - which are the only two runway surfaces options in my 340’s performance charts - and the published rotation speed of 91 knots may be slightly on the high side if you're operating at very light weights. For instance.

I was considering the possibility that the risk might be basically double that of a single - ie that if you have an engine failure at slow speed, you may accept that you are going down, but straight, level, and in control, but the chances of an engine issue are, of course, doubled. If it was the case that a well handled engine failure, at worst, involved a controlled level crash/overrun, well, that's one thing, and worth considering in terms of operating out of the field I’m considering, which, by the way, is 2400 feet long, so it’s short for a 340, but possibly not exactly a postage stamp. If a VMC roll is inevitable, likely, or even possible, then of course that's a whole different ball of wax. This is what I've been trying to find out. In between the invective, there's been a lot of worthwhile discussion, and I thank you guys for that.

Angry poster guy quoted me on a different thread as "(postulating) that as directional control may not be available on the ground after an engine failure, he sees no reason why one should not take off below Vmca." This illustrates one of the limitations of written communication in general, and particularly where goodwill & respect aren't present. What I actually said was

"What I don't understand is why, if you were hair-triggered to cut power on the live engine, as close as humanly possible, as well as applying immediate opposite rudder (aileron?), then wouldn't the removal of the live power remove the roll/yaw immediately, and thus turn it into a common-or-garden engine failure situation? "

The key being "I don't understand why". I didn't say that I DO understand why, I said I DON'T understand why. I also didn't say that I take off below VMC (I don't) nor that I plan to (I don't.) I was trying to answer a question that I confuses me, and I’m sorry to say I still don't really understand. My original question was “Anyone know what the shortest possible/reasonable/safe takeoff would be for a 340 operating at very low weights?”. One of the posters on the thread has kindly PM’d me with a concise and reasonable answer to that particular question. If I somehow conveyed an intention to fly unsafely, well, it was unintentional. Again, written language, without the non-verbal cues & feedback of a conversation, is easily misinterpreted, which is why I think it’s important to read these anonymous posts with goodwill and an open mind. But having answered that question, I’m STILL not sure why you can’t cut the power on the good engine, and end the assymetric thrust issue, turning your engine failure into a double engine failure, but at least going in under control, and right way up.

Yes, I've read this thread several times, and I understand the definition of VMC ".........critical engine suddenly inoperative with the working engine at maximum rated T/O power in T/O configuration (=gear up)", and I understand why that leads to roll and yaw that cannot be overcome. But I still don't understand why that roll and yaw could not be stopped when you cut power on the operative engine, unless rote adherence to procedure qualifies as understanding. In my experience, I would estimate that power reduction on the good engine would take a about a second or so to take effect, not the four or five seconds referred to by one of the contributors to this thread. (And, of course, the failed engine is likely to spin down at a similar rate, rather than stop dead.) I would have thought that the immediate power reduction, COMBINED WITH opposite rudder/aileron (which will, of course, be effective to some degree, just not enough to overcome the yaw & roll moment of a "working engine at maximum rated T/O power" might, in fact, be enough to prevent the yaw/roll combination that could induce a VMC roll.

I realise that what I "would have thought" isn't enough basis to go and fly the machine in a manner different to that written down in the manual. I'm not suggesting I'm going to. I'm trying to educate myself here. I am mystified by the concept that "conflict hones the skills and allows everyone to reasses their values and opinions". Personally, I find that reasonable discussion is a more effective route to reassessing "values & opinions" than trading barbs about how stupid someone is. And, of course, training in the aircraft - and in the simulator, where some scenarios are too dangerous to enact in the real aircraft. I am indeed heading off to Flight Safety, and will continue to explore the questions raised in this thread, in a safe manner.

It's a shame that these threads, which can be so educational, so easily degenerate into people talking to each other in a manner that I doubt very much they would do so mano o mano, so to speak, unless they were drunk. Actually, maybe that explains it!!! Maybe some of these guys are drunk! I see now :)

So. I have a great deal to think about. As it happens, VMC on my aircraft is about the same as the stall speed, due to the vortex generators, so it may be that I don't need to even think about this issue. And according to the published charts, the field, at 2500 feet, is long enough for operations at light weights, provided the (grass) surface isn't too soft, and with the caveat that “balanced field” ops aren’t possible. But we'll see. In terms of real world actions, from here on in, I am indeed going to attend a Flight Safety course, where I hope it may be possible to accurately simulate a light weight 340 with VGs operating off a grass field. I doubt if I'll posting the video for Lifeisgood & his friends to scoff at over their beers, but yes, videoing it for later review is a very good idea, and I will do that. I'll then, before I even think of flying out of this particular field, do plenty of flying off a l-o-n-g grass runway, to get completely current on the performance of the machine at light weights. As it happens, whatever misunderstandings angry poster guy et al may have come to, I quite agree about the need for safety in all aircraft operations. And if I have somehow suggested things that seem to belittle airline pilots and airline operations, well, I apologise for that. It wasn’t my intention. I think the safety record of the airlines is outstanding, and that private ops should indeed aim to be as safe as possible. It is my **personal opinion** that many PPLs do have more freedoms and privileges than many airline pilots, in that we are the sole decision-makers, within the bounds of legal regulations, when it comes to go/no-go decisions, routes flown, airstrips/airports used, weights flown at, fuel carried, (often) maintenance carried out/deferred and so on. I’m sure that’s one of the many reasons that private flying has a worse safety record than the airlines, not that I have ever said I think that’s a good thing. Note, however, that I didn’t say that PPLs have more responsibility. Obviously flying with 50, 100, or 300 people’s lives in your hands involved a great deal more responsibility than when you’re just dealing with your own life, and perhaps those of your family and friends.

So thank you, y'all, even angry poster guy, for your responses. There is indeed a lot of wheat amongst the chaff. You've all given me lots to think about, and no, I won't be racing off to kill myself in my 340.

[Lifeisgood]

I can tell you that I have attempted Vmc demos in my 340A last year at a safe altitude, 10,000 AGL, just to see how it would behave. I trained in the venerable Beach Duchess, and as benign as she looks, she can be a handful if you push the power in too quickly in the Vmc recovery maneuver. I once had a Duchess with wings almost vertical in less time than you can say “OH ****”. I quickly learned you ease the power in, don’t cram it. Anyway back to the 340A in a Vmc demo.

I could not get the 340A to roll.

There was adequate rudder and aileron control right down to a stall buffet at about 78 kts! I was configured at GTOW less 800 lbs, which should have raised Vmc, I was also at 10,000 Ft AGL, which I do not think affected the Vmc Demo because the turbochargers compensated for DA with the engines and the airspeed indicator and wings simply compensated for the DA via indicated airspeed. At this point I conceded that the Vmc was below stall and did not wish to become a test pilot doing spin recoveries in my favorite twin. It would be interesting to know if a Simulator can be configured at a lower weight than MGTOW and if the flight characteristics will be modified to that minute detail, I doubt it.

I can also tell you the improvements in performance in a 340A when lightly loaded are spectacular. In my 340A with just myself and half fuel it’s a rocket on takeoff. I usually see in excess of 2,200 fpm on takeoff.

So the short answer to; can it be done; yea, probably.

Should you do it; only by yourself.

But the better question is; why would you want to?

In retrospect, the negative comments you received were doubtless due to a few pilots expressing their dismay, me included in that group, of you suggesting a very high risk maneuver. You are responsible for your decisions, and you certainly seem to be well trained in all pertinent aspects of this flight envelope. To attempt a takeoff below Vmc is contrary to the POH and countless other rules, regs and best practices. You asked for advice on an unsafe, foolish maneuver and received chided demonstrative responses you did not appreciate. Go figure. The entire aviation industry and culture is invested in safety, training and sound piloting. The 340A is not a short field aircraft, to attempt to use it as such is placing it a flight envelope it was not designed for and is not a sound decision.

That having been said, Best Whishes.

[SNS3Guppy]

I can tell you that I have attempted Vmc demos in my 340A last year at a safe altitude, 10,000 AGL, just to see how it would behave.


How the airplane behaves at 10,000' and at sea level, particularly on takeoff, will be two very different things, particularly as effective Vmc (the actual speed, rather than the certification number) decreases with altitude.

In retrospect, the negative comments you received were doubtless due to a few pilots expressing their dismay, me included in that group, of you suggesting a very high risk maneuver. You are responsible for your decisions, and you certainly seem to be well trained in all pertinent aspects of this flight envelope. To attempt a takeoff below Vmc is contrary to the POH and countless other rules, regs and best practices. You asked for advice on an unsafe, foolish maneuver and received chided demonstrative responses you did not appreciate. Go figure. The entire aviation industry and culture is invested in safety, training and sound piloting. The 340A is not a short field aircraft, to attempt to use it as such is placing it a flight envelope it was not designed for and is not a sound decision.


Well said, and that said, sometimes one simply cannot give a drowning man a glass of water.

[Big Pistons Forever]

Lostpianoplayer.

From my point of view the real issue in this thread should not be how to squeeze a C340 into a role it was not designed for but rather what aircraft meets your operatonal requirements of

1) be multiengine

2) operate out of a 1600 ft strip at 2500 MSL with 1 or 2 pasengers

3) can be safely operated by a relatively low multi time pilot

I would suggest you should look at a Roberston STOL turbo C337 skymaster.
This aircraft would in my experience meet all your requirements and of course does not have the VMC issue.

[bookworm]

In both the single STOL situation, and taking off in a piston helictoper - or for that matter flying over, say, forests, in either, one is frequently in situations where an engine failure at an inopportune moment could cost you very dearly indeed. The scenario you paint, in terms of a STOL takeoff in a twin, doesn't seem entirely dissimilar, to me, than that of taking off in a single – EXCEPT for the VMC issue.

I think the difference is that in the single, in the case of a non-catastrophic engine problem, you leave the throttle fully forward and fly the aeroplane. You probably look for somewhere, or a selection of sites, to put it down straight ahead. If you're still climbing, bonus, the engine failure wasn't as bad as it might have been and you keep climbing. If the engine loses power completely, you're going to glide to a landing site as best you can.

In the twin, you really have the decision to make, right then and there, before you have much chance to properly assess the problem. If you don't make the decision to close both throttles, and the engine goes on to wind down to complete failure, you're flying yourself into a loss of control.

By contrast, in a similar situation in the climbout at Vyse or above, you have a little more time to assess the situation, and, just as in the single, can afford to leave the problem engine running to see what happens. Of course you can't wait forever, but you're not going to shut it down at the first cough at lowish level if there's a very good chance that it will still be producing useful power.

[Big Pistons Forever]

Lostpianoplayer.

From my point of view the real issue in this thread should not be how to squeeze a C340 into a role it was not designed for but rather what aircraft meets your operatonal requirements of

1) be multiengine

2) operate out of a 1600 ft strip at 2500 MSL with 1 or 2 pasengers

3) can be safely operated by a relatively low multi time pilot

I would suggest you should look at a Roberston STOL turbo C337 skymaster.
This aircraft would in my experience meet all your requirements and of course does not have the VMC issue.

[lostpianoplayer]

Bookworm, re getting airborne w a questionable engine, I guess my point was just that the same thing could happen in STOL operations, where you have to make a quick decision about taking it airborne with a POSSIBLY malfunctioning engine, but as you're rapidly accelerating on a short field, a true short field, you have a millsecond to cut power and brake, and possibly still go through the fence at the end. OR get airborne with a problem that could get a lot worse, very fast. I'm not saying this is a good thing, just that the phemenonon exists, and people nonetheless operate STOL in singles. I can see how it could be more of an issue in a twin, at least in part cos you have more coumns & rows in the decision matrix.

Re the choice of machine, BPF, thank you, and yes, you're right - a turbo Skymaster WOULD be a good strip machine. But the 340 fills other needs/desires I have, very well, and I have other aircraft to use for the short strip role. I've always been prepared to base the 340 at the local airport (runway 5000 +), but have been trying to get a thorough understanding of WHY, not really WHETHER I shouldn't base it at my own (shared) private airstrip, which, at 2500 feet long, is not a short strip for many machines. (The 1600 feet referred to in my first post, incidentally, was published takeoff for a 340 at full gross, not the length of the airstrip.) My instructor & flying mentor, with whom I have been flying for 12 years, and I didn't have a clear consensus on the VMC issue, and I decided to ask here to advance our own knowledge. We'll be discussing this issue over dinner some time, and he was a little hazy on some aspects of VMC himself, despite having telephone number hours in all sorts of different aircraft. I'm not, and was never, looking for ammo with which to veto his advice - just to find out more, and UNDERSTAND the situation. Especially as I was told when training, that the first thing you do to stop a VMC roll was to cut power - which would obviously improve the situation to some degree. The question is how much. It sounds like some are of the opinion that a VMC roll, once started, is unstoppable, and I hear ya. I'm not sure I agree (yet), but will take this issue further. I'll certainly do my best to see if the good folks at Flight Safety will demonstrate it all to me, and have no doubt that they'll be happy to do so. So yeah, thanks for the suggestion of a more suitable machine, but that's not really what it's about. It'll be a long runway for me & the 340, for the forseeable future.


Re dismay, drowning men, glasses of water, etc, well, whatever. A lot of what I wrote was taken out of context or misunderstood, interpreted in its worst light, or whatever. Partly my fault for pasting over a question from a different forum, and mixing up practical questions like question (1) (what is the shortest reasonable/possible/SAFE takeoff, ***which by definition means ABOVE VMC***) with theoretical questions like question (2). IF (IF!!!!) you took off slow, and had a failure, then why wouldn't retarding the assymetric power stop the roll/yaw.) I'll make sure that if I venture over here again I'll keep the questions very simple, don't confuse the thread with multiple questions, and make sure that I make the caveats, context & exceptions clear. BTW, Guppy, the whole POINT of "taken out of context" is that one IS, indeed, "quoted". But quoted without the context, as you'll see on the news every day, can totally distort the meaning. One aspect of this thread which I find very interesting, is that written language is so limited, and can be easily misunderstood, either in tone or in substance. You could consider my two first questions, for instance, and pretend just for a moment that the person who wrote it has no intention of taking off subVMC, or anywhere near it, unless he can be satisfied that a VMC roll can be stopped by retarding the other one. And he doesn't understand, at that stage, why it CAN'T be stopped by retarding the power on the good engine. Maybe the questions might be seen in a different light then, rather than their author 'planning to do something really dangerous', 'condemning safety' and so on. (Only do this if you find linguistics enlightening, and don't actually get off on having unncessary arguments, which of course, some people do!) I don't care about my aviation reputation amongst a few anonymous computer users - I just think the aggressive tone obscures what is often very helpful substantive information and opinions. And I find it fascinating how easily information can be & is misinterpreted or twisted. It demonstrates, for instance, the limitations of flight manuals, per se, without clarification & further training - or the reason that angry emails to, say, your employer tend to backfire. Effective communication relies heavily on context, clarification & feedback. Anyway. I think we're well beyond the 80/20 on this thread, and this time I really am gonna sign off, unless something takes an interesting turn. Feel free to PM me if you want to take things further - and thanks, really, to the people who have PM'd me about the questions I asked at the beginning, with what has been a helpful boatload of information, and also to everyone who's contributed to my understanding of this issue. Particularly those who provided real world 340 data even if they may have misunderstood the point of my questions, and my intentions. Fly safe, and cheers.

[Lifeisgood]

Regarding “if Vmc speed reduces as altitude increases”. I pondered this question for a quite a while, discussed it with knowledgeable CFI’s and commercial pilots and would appreciate input from others.

Is this true in a turbocharged aircraft or for that matter any aircraft that is flat rated to a given altitude? I believe this generally held belief is due to DA decreasing with altitude and consequently less air molecules available for combustion, and therefore less power produced, and therefore less torque, and therefore a lower Vmc speed in non-turbocharged aircraft.

Regarding the wings; Because DA reduces with altitude there are less molecules of air hitting the front of the Pitot tube, so therefore we are trained to understand and use indicated air speed, IAS. Or to paraphrase, IAS is always used by pilots because IAS automatically compensates for DA. Therefore as pilots we understand that IAS is not TAS but to use IAS for all maneuvering decisions and understanding that true airspeed is higher due to effects caused by DA.


As per WIKI.
“Unless an aircraft is at sea level under International Standard Atmosphere conditions (15°C, 1013 hPa (http://en.wikipedia.org/wiki/Pascal), 0% humidity) and no wind, the IAS bears little relation to how fast an aircraft is moving in reference to the ground; however, because the air pressure and density affect IAS/CAS and an aircraft's flight characteristics in exactly the same way, IAS and CAS are extremely useful for controlling an aircraft, and the critical V speeds (http://en.wikipedia.org/wiki/V_speeds) are usually given as IAS. In aneroid instruments the indicated airspeed drops-off with increasing altitude as air pressure decreases, and this leads to an apparent falling-off of airspeed at higher altitudes.”

So the question is;

Does the IAS Vmc speed reduce in an aircraft that has flat rated engines as DA increases?

Opinions appreciated.

[Big Pistons Forever]

Lostpianoplayer

I did C340 recurrent training in SIMCOM's sim. I found the sim very accurately replicated the flying qualities of the real airplane. It was hands down the best training I have ever done for light aircraft. I got to see every possible ugly takeoff scenario you could think off. This is what led to the personal decison to delay rotation to 100 kts as I found I could fly away every time. I hope you enjoy your time at Flight Safety. One note of caution. My buddy the high time owner of the C340 I used to fly was rather unhappy with the instructor he had at FS last fall. She was very inexperienced and would not deviate from the check box training form she was given. I would recommned you discuss what you want to do in your training with Fight Safety management before you arrive in order to ensure you get an instructor who will give you what you want. You should also compare SIMCOM's program before making up your mind.

[SNS3Guppy]

Is this true in a turbocharged aircraft or for that matter any aircraft that is flat rated to a given altitude?


Yes, it's true, but the decrease in the effective minimum single engine control speed (which isn't the same as Vmc...Vmc is a certification number) isn't as large with a turbocharged, supercharged, turbosupercharged, or turbocompound engine.

The engine can only output so much, and regardless of whether the engine output remains the same (a turbo normalized engine, for example), the propeller efficiency decreases with altitude due to a decrease in air density. Less thrust, less assymetrical thrust, lower real minimum single engine speed required to achieve the same result.

Remember that Vmc is a function of assymetrical thrust, which is an indirect effect of engine performance. The engine still has to turn the propeller, which must act on the atmosphere to produce that thrust. Decrease the thrust (a function strictly of blade angle, air density, and RPM), and you decrease any potential for thrust assymetry, and therefore the value of "Vmc" decreases. Just the same as if you reduced power on the good engine.

Vmc is a solitary number, and in most cases, it doesn't go up or down appreciably. Some AFM's publish variable numbers, but it's generally given as just a red radial reference line on the airspeed indicator. That aircraft control is actually lost at this point is merely a coincidence. Numerous factors can decrease the actual speed where directional control isn't possible, and various factors can increase the number...all while Vmc remains the same. Actual performance isn't the same as Vmc. Vmc is a paper number, not what's going on in the airplane.

We generically refer to what's really going on in the airplane as Vmc to make it simple, but this also tends to confuse the issue sometimes when talking about the science behind it.

I believe this generally held belief is due to DA decreasing with altitude and consequently less air molecules available for combustion, and therefore less power produced, and therefore less torque, and therefore a lower Vmc speed in non-turbocharged aircraft.


Density altitude increases with altitude, and with an increase in air temperature. It does not decrease with an increase in altitude except in the case of a strong temperature inversion, and then only for brief periods.

Regarding the wings; Because DA reduces with altitude there are less molecules of air hitting the front of the Pitot tube, so therefore we are trained to understand and use indicated air speed, IAS. Or to paraphrase, IAS is always used by pilots because IAS automatically compensates for DA. Therefore as pilots we understand that IAS is not TAS but to use IAS for all maneuvering decisions and understanding that true airspeed is higher due to effects caused by DA.


The wing is irrelevant to the question, because Vmc is a function of assymetrical thrust and control availability (chiefly rudder). Center of gravity makes a difference, but the reason the minimum control speed decreases with altitude (again, DA, or density altitude does not decrease with an increase in altitude) is a decrease in assymetrical thrust. This is more pronounced in a normally aspirated engine, but still exists in a turbocharged engine for the reasons previously given.

Does the IAS Vmc speed reduce in an aircraft that has flat rated engines as DA increases?



Again, Vmc may never change, because it's a single number, and is painted on your airspeed indicator. The actual number at which directional control can no longer be maintained (the effective Vmc, if you will), does decrease...even if the engine is normalized to maintain the same power output as altitude decreases. The engine still has to drive the propeller. The engine doesn't produce any thrust of it's own accord (save for a few circumstances where exhuast gas does produce a very slight thrust quotient). It's the propeller doin the work moving the air, and it's propeller efficiency that decreases with altitude.

Additionally, while one flies the same airspeeds with an increase in density altitude, as one climbs the air density and aircraft reaction does not remain in proportion. This isn't greatly noticable at lower altitudes, but it is the higher you climb.

[bookworm]

The engine can only output so much, and regardless of whether the engine output remains the same (a turbo normalized engine, for example), the propeller efficiency decreases with altitude due to a decrease in air density.

I don't doubt that propeller efficiency plays a part. Also worth remembering that power is thrust x TAS. For the same IAS, TAS is higher at higher DA, therefore thrust is less for an engine flat-rated to a power.

[Lifeisgood]

I’ve read up on propeller efficiency loss at altitude, there seems a lack of readily available information on this. As a matter of curiosity I would like know what percentage of loss occurs from sea level to FL200 for a constant speed propeller. In my previous article I mentioned wings being affected by DA, I should have said airfoils, which includes the rudder. Meaning that all airfoils are affected by less wind crossing their surfaces and eventually control is lost.

This is all a moot point, because we are talking about controllability at the edges of the envelope. To know which force will cause the Vmc roll is hardly necessary; is it the lack of rudder, the roll from loss of aileron control, the torque of the engine or a concert of forces working together to kill the pilot and passengers.

The best practice, and that which we have all been taught, is to avoid these death traps with prudence and good piloting skills.

This has been an enjoyable but somber rant.

Adieu

[Big Pistons Forever]

Last week a well maintained corporate C421A went off the runway at my home airport. Loss of control was caused by a broken scissor bolt which allowed the right main wheel to rotate 90 deg. It is in the shop waiting for a whole new gear set as all the legs failed NDT inspections. The pilot felt a contributing factor my have been its regular operation into a sea level 2400 ft paved strip. This invariably required firm touchdowns and immediate very heavy breaking. As twin Cessna's have a well known reputation for weak landing gears perhaps this is another reason you do not really want to be forcing them into short strips.

WRT the rather arcane discussion on prop efficency and VMC I second lifeisgood's sentiments. It is all about not going anywhere near the edge of the cliff. In any case my expereince has been that the all of the scary moments in my approx 2000hrs of instructing invariably involved instructing low houred PPL/CPL's for the ME rating (a total of maybe 60 hrs of the above 2000hrs). it sure gave me a healthy respect for the dangers of one engine operations in the low speed regimes :eek:

[SNS3Guppy]

On the subject of instructing the multi engine student, I have always practiced blocking the rudder pedal during single engine work such that the student does not have full rudder throw available. In the even the student doesn't react quickly enough or properly, the remaining rudder throw is mine to maintain control and recover.

[DirtyProp]

Hi folks,
I'm resurrecting this old dog for a specific question regarding the 340. I came across a decent one recently, which is collecting dust and the owners don't know what to do about it.
The pilot told me that it flies great, however it has a persistent problem with the fuel pumps transferring fuel from the aux to the main tanks. The pumps short all the time, thereby rendering the aux tanks unusable and shortening the range considerably.
Is it a know issue of this type?
Many thanks in advance.

[Pilot DAR]

Two things come to mind with this situation. It's been 35 years since I've flown 340/310, so I'm going from old memory, but; the aux tanks are selected by the pilot with the fuel selectors, rather than pumped. The engines are either running from the mains (tips) or the aux (wings), there is no transfer aux to main. Note that if you're flying off the aux tanks, excess fuel from the aux tanks will be returned to the mains, rather than back to the aux tanks from where it originated. If the plane has wing locker tanks, they would be pumped to the mains, then burned from there, though they are comparatively small capacity. There are also pumps which pump the fuel within the tips. So, I suggest confirming exactly the configuration of the fuel system.

Then, more basically, if a fuel pump is not working, or worse "shorting", the plane is unserviceable, it should be repaired before further flight. The fuel pump electrical circuits are simple, so there should be no complex reason they're not working. If the reason is complex, the plane has a bigger problem. For what it's worth, I attended an aging aircraft presentation at Cessna in Wichita many years ago, focusing on the 400 series (but equally applicable to the 300'S). Though the presentation would have been expected to be mostly about structure, the presenter said that major defects were common in electrical systems, and aged electrical systems require extensive inspection and testing for condition, and correct operation.

If you're asking this because your considering operating/owning the plane; the 340 was a wonderful plane in its time. It's now an older plane, and subject to many burdensome inspections. That doesn't make it a bad plane now, but a more burdened, and expensive plane to operate. Thoroughly understand the plane before you accept responsibility for operating costs.

[Big Pistons Forever]

I am current on the Cessna 340

it has up to 9 electric fuel pumps

2 in each tip tank, one to pump fuel from the back to the front of the rank and one to provide fuel pressure to the engine for priming and in the event of an engine driven fuel pump failure

1 in each wing to provide positive pressure and vapour suppression when the engines in feeding from the wing aux tank

1 in each wing to provide pressure to transfer fuel from the nacelle tank (if fitted) to the tip tank

1 in the nose to provide fuel pressure to the cabin heater

The fuel system is very complex and a full understanding of it is essential in order to safely operate this airplane. Depending on what pump has failed it can be a nuisance (eg no heat) to flight safety critical (engine failure)

As a general comment airplanes which have sat for a long time are often maintenance nightmares. I once ferried a Cessna 421 home for its new owner. The aircraft had a similar history to what you described. The snag list when I got it home had 59 items. For the first 6 mon5s it was in the shop after every flight. Eventually after a lot of hassle and expense the aircraft was brought to a reliable state but it was frustrating and painful. Even though the owner got a smoking deal on the airplane he vowed never again....

[DirtyProp]

Many thanks to both of you, much appreciated.
I know next to nothing about the 340 and I don't know the full story of this particular bird so I simply reported what the pilot told me, but it's possible that I misunderstood. I will make sure to study the POH thoroughly next time.

It seems to me that generally speaking it's a very capable airplane, able to operate from grass runways without problems. But obviously bringing it back in line will probably be a financial nightmare. What would the dispatch reliability be, if anything was in order?

[Pilot DAR]

I flew the 310 lots, and the 340 a little, they're pretty well the same plane, cabin and pressurization being the differences. Reading the POH, though very important, will not be enough, get some specific type training from a 310/340 experienced pilot. Though I'd flown Aztecs before, I did my formal multi engined training on the 310, with a very experienced 310 pilot. Thereafter, after some searching, I found an examiner to give me my multi engine rating on the 310, and I was glad I had. He know things about that plane which I learned during the ride. And, he knew things about it which allowed me to pass the ride even though it wasn't quite by the book - because the 310 was not quite by the book either. He knew that, and allowed for it.

The fuel system is excellent, and I really liked it, once I understood it. In hind sight, the six tanks, and requirement to manage fuel was preferable to the two tank system of the 303 which I later flew, and did not like anywhere near as much. All of that vintage of Cessnas are now subject to inspections more burdensome than those with which the plane was originally certified. These inspections are expensive, but necessary. Though I did fly the 310 off grass, it was really smooth grass. 310/340 gear (the same) is not borne for rough field, nor short field operations - that's where the Aztec had it over the 310. I had gear problems with the 310, and they were never corrected with complete confidence. I see twin Cessnas for sale at very attractive prices, and I know why. When a twin Cessna is offered for sale at a lower price than a Cessna single, there's a message in there for you. If you really need the second engine, okay, but you're going to pay for it! Let alone the second engine, there are many more systems, and things to fix. The plane was never manufactured to be economical transport this long after manufacture. The fact that they are still flying is due to owner dedication, and money - understand the costs! Sure, if the plane is given extensive maintenance, it'll be great. If the task and utilization justifies that, super! But, they are never a "deal" to fly because they are older.

Really do your research on this type...