Light twins - single-engine climb performance
 

Hi,

Does anyone know if there are any legal requirements to achieve any particular single-engine climb performance in a light twin - preferably on-going requirements, but otherwise requirements for a new-from-the-factory aircraft?

The aircraft I'm specifically interested in is a Beech Duchess, so I imagine it would have had to have passed FAA requirements when it was new. It's now on the G register, so JAA requirements would be useful too. What I'm specifically looking for is something which I can either show to an engineer and say "this aircraft does not meet this requirement, therefore it needs fixing", or alternatively show to a pilot and say "this aircraft meets this requirement, so it's ok to fly".

Thanks!

FFF
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Aha - I might have just found the answer. I took a rare visit into the Flight Testing forum, and found this thread, with this link. If I read it right, the answer to my question is that, because Vs0 on my Duchess is less than 61kt, there is no climb requirement. Have I got that right?

FFF
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Hello Flying for Fun,

All the information you're looking for can be found in FAR23.66 "Takeoff climb" and the other nearby paragraphs. If it is an earlier aircraft, CAR 3 standards might apply, but they are quite similar. FAR23 should be easily found on various websites. It is certainly on the FAA website, but not easy to find.

Do not expect to just go out and perform such a test. It requires a lot of precision to get an accurate result, and would be UN-NECESSARILY UNSAFE to test close to the ground. If the plane otherwise flys in trim, seems to handle properly, and has proper control travel available, the only other consideration for poor performance would be engine(s) not developing adequate power. Climb testing of any kind is probably the least effective way to diagnose engine power problems. Most of that kind of investigation is done on the ground by maintenance staff.

Cheers, Pilot DAR

Can't help you on the reqs really, but I have some other input that you may want to consider.
One of Sweden's largest schools, training hundreds of pilots per year, uses the Duchess for ME training. They have specific operating procedures that keeps them far far far far away from stall conditions at any point of flight in that particular aircraft type. The Duchess is considered vicious close to stall and especially on one engine. In general single engine climb performance will be poor.

An aircraft fit to stay clear of...

Having raised myself reading stories of Beauforts, Beaufighters, Mosquitos etc going into uncontrollable yaw/roll modes if they lost an engine on takeoff, could anyone who actually drives light twins tell me what it's like these days if you lose one engine just when you've left the ground? Is it ever practised or is it better avoided?

Just out of curiosity you understand.

If you know what Performance Category the a/c is in, you'd be able to find any climb requirements in JAR-OPS (or the FAA etc. equivalent) in the corresponding section.

V1R :ok:

Sedbergh,

I fly PA34 Seneca aircraft and we often practice engine failures after takeoff (usually at about 200' AGL) and they are, by necessity, perfectly managable. Speed control is important though - if you drop below Vmca (minimum control speed with one engine inoperative), you run the risk of not being able to maintain directional control, even using both rudder and ailerons. At altitude you could pitch down to speed up again and thereby get control back but you'd have limited options near the ground :bored:

V1R :ok:

Ta Vee

hoped it must be something like that! I've always wondered slightly about small twins. I used to get flown out of Nairobi in a Partenavia P68 - grand until the pilot told me one day what height it would level out at, fully loaded on one.

A lot lower than Nairobi!:{

Yeah, wouldn't like to get into certain corners in a Seneca either.

In a hot climate, even moderately loaded and at moderate altitudes, when you bin an engine in the cruise you're sometimes forced to drift down as you can't maintain altitude, even with the Seneca's twin turbos :(

Of course, it was always in the name of practice and we weren't MSA-limited!

V1R

From memory (which is fallible), and its been a few years since I flew the Duchess, I think its perf E, but don't put any money on it :}

Brooklands

Does it have to perform at all? Most Duchesses I have flow have crap SE performance, just like most training aeroplanes (Seminole for ex).

I'd use the SE ceiling, as ceiling is defined as rate of climb of less than 100 fpm. If the SE ceiling is low, (4000' ish) as it is for many light twins then I'd assume it wouldn't climb. Some are better than others, for example the Seneca II will got o 13,000' on one engine by virtue of the turbos.

Of course if you drop below Vmc and you don't have height to loose the ONLY thing you can do is reduce power or else you are dead. Part of the FAA ME rating is to perform a Vmc demo (at height ;)) where you fail and engine, then go full power on the other and pitch up to let the speed decay to below Vmc. The thing that surprised me was the speed at which you loose it when it goes.

Unless it is a turbocharged aircraft Vmc is a bit academic "at height" as the live one won't be developing anything like 100% power.

Did the instructor/examiner wedge something (their foot for example) under a rudder pedal to simulate loss of rudder authority at "Vmc", or did you actually allow speed to go well below Vmc and therefore close to stall speed - which engine out is fairly exciting.

Surely the answer is "the Approved Flight Manual". I don't know what the tolerances are for SE climb, but if it doesn't do what the AFM says it does, it needs fixing.

You will do them on your initial MEP.

You will probably do them on your renewal.

Depending on the twin the performance varies significantly as does handling for all the usual reasons concerned with where the engine is mounted and which one it is, or whether it has rather nice counter rotating props.

I dont think things have really change with "modern" twins - not that there are very many. The DA42 at MTOW has little performance reserve and because rather like most modern aircraft the airframe is "slippery" to extract the most from low powered engines managing the aircraft on one engine is critical. At MTOW in my opinion you need to be right on the ball should the worst happen at the most critical time and it could easily catch out a rustle or low time pilot.

Yep true. Isn't it called Coffin Corner where Vmc and stall coincide?

It was a Seneca II and so was TC'd (actually develops more HP at altitude than sea level). The examiner didn't wedge his feet under the rudder pedal then, though I believe now they are advised to do so nowadays. I think I would if I were an examiner ;) I chatted to one FI who lost 5000' in a Vmc demo gone wrong....:eek:

Regarding the DA42 - we failed one engine at 5000' in California last year. The weather was reasonably warm, we had lots of fuel (long range tanks) and 3 blokes with overnight baggage onboard. The thing perfomed amazingly and we had no problem climbing at all....(being TC'd helps of course).

WTF is that supposed to mean? :hmm:

You are only legally required to have single engine climb performance when operating commercially and in a situation where you can not see and avoid obstacles.

Since you are probably providing training for the CPL then the requirments of JAR-Ops for perfromance class B are appropriate for understanding the situation.

In terms of "is this aircraft performing correctly" then the reference is the flight manual which will schedule the gross performance that the aircraft should manage.

Apply your factors to get net performace and confirm that the aircraft is meeting those requirements with ease.

I would not use the certification standards to confirm performace of an established aircraft as the aircraft may have be designed to exceed those minimum performance standards and while grossly underperforming may still meet the minimum requirement.

The flight manual is your legal guide. The Manufacturer will also help.

The friendly pilots at the CAA flight test department will also help you with a better and more specific answer.

Regards,

DFC

Not traditionally, no. The Coffin Corner is something else entirely.

Nathan is correct. Coffin corner is a situation when you cannot go slower nor faster without stalling or exceeding speed limits. Typically a problem with swept wing jets that climb high enough that stall and Mmo coincide.

With regard to Vmc and stall, it isn't a corner because you only need to increase speed to get out of it.

I'm pretty sure it's supposed to be a compliment, saying that you are a high time pilot and not normally easily caught out. ie. you're the contast to the low time pilot.

People find insults anywhere they can :rolleyes: Are you sure you're not an ex g/f of mine? :p