Complex and High Performance checkout

[Berkut]

So max continuous at altitude is more then max allowed for takeoff?

Yep.

You can download the TCDS here: http://rgl.faa.gov/Regulatory_and_G...79578854D89E712286257209007693D4?OpenDocument
Scroll down to the PA-34-200T (Seneca II) engine limits, and it says:

Engine Limits
For all operations, 2575 r.p.m. and 40" Hg. Manifold pressure, 200 hp @ S.L. and 215 hp @ 12,000 ft.

In a Seneca II, the same RPM/MAP setting gets you 200HP at sea level, but 215HP at 12,000 feet.

So does the Seneca II require a high-performance endorsement?

An even better question is, why the heck does the Seneca II put out more power at 12,000 feet than it does at sea level with the exact same RPM/MP settings? Answer that one and you'll win... well, nothing, but I'll be impressed.

 

[Cessnaflyer]

I would like to see the answer also. Nothing right now logically adds up in my head.

 

[tgrayson]

So does the Seneca II require a high-performance endorsement?

The FAA in the defunct Part 61 FAQs said "yes".

An even better question is, why the heck does the Seneca II put out more power at 12,000 feet than it does at sea level with the exact same RPM/MP settings? Answer that one and you'll win

Reduced exhaust back pressure?

 

[butt]

So does the Seneca II require a high-performance endorsement?

I'm pretty sure you do. The only plane my father has ever flown, is a C172 and a PA-34-200T, and I'm pretty sure he has a high performance endorsement. I'd call him but he lives in another time zone.

 

[Berkut]

Reduced exhaust back pressure?

You're the man.

 

[Cessnaflyer]

reduced back pressure seems logical to me!

Now would the engine performance be greatly increased if it just came straight out of the exhaust port?

 

[Cruise]

Yep.

You can download the TCDS here: http://rgl.faa.gov/Regulatory_and_G...79578854D89E712286257209007693D4?OpenDocument
Scroll down to the PA-34-200T (Seneca II) engine limits, and it says:In a Seneca II, the same RPM/MAP setting gets you 200HP at sea level, but 215HP at 12,000 feet.

So does the Seneca II require a high-performance endorsement?

An even better question is, why the heck does the Seneca II put out more power at 12,000 feet than it does at sea level with the exact same RPM/MP settings? Answer that one and you'll win... well, nothing, but I'll be impressed.

The FAA in the defunct Part 61 FAQs said "yes".

Reduced exhaust back pressure?

Ok, I'm feeling much better about the high performance endorsement I received for the Seneca II. I knew my instructor (at the time) told me the engines put out more than 200 HP at altitude, thus requiring a high performance endorsement.

Not that it matters now...but, it's good to know he was right!

 

[Swen]

Ok, I'm feeling much better about the high performance endorsement I received for the Seneca II. I knew my instructor (at the time) told me the engines put out more than 200 HP at altitude, thus requiring a high performance endorsement.

Not that it matters now...but, it's good to know he was right!

Add me to the list. I got my HP in a -200T and was getting ready to faint reading this thread...

 

[tgrayson]

Add me to the list. I got my HP in a -200T and was getting ready to faint reading this thread...

Here's a copy of the FAQ:

QUESTION: Is a Piper Senaca II a high performance airplane. The Piper Senaca II AFM says its engines are rated at 200 horsepower at sea level and increase in altitude up to 215 horsepower at 12,000.

ANSWER: Ref. § 61.31(f); It is a high performance airplane. The rule states, in pertinent part, “ . . . (an airplane with an engine of more than 200 horsepower) . . .” And as you stated, the Piper Senaca II is “an airplane with an engine of more than 200 horsepower.” The rule does not differentiate where the engine has to be more than 200 horsepower, it just says “an engine of more than 200 horsepower.”
{Q&A-59}

 

[PanJet]

That's certainly very interesting, and I did not know that about the Seneca's being high performance. I apologize to anyone for my misinformation. You learn something new every day!

On a side note, I looked up the TCDS for the Turbo Arrow, and it does not list the same HP increase as the Seneca II (therefore it is not high performance). In fact, so far as I've seen, the Seneca II is the only plane that has this increase. Why is that?

 

[Berkut]

Now would the engine performance be greatly increased if it just came straight out of the exhaust port?

Well, I wouldn't say greatly. We can't do that with a turbo system anyway.

The FAA allows 2 in/Hg of backpressure from a stock exhaust system. We lose 1% of horsepower for every 1 in/Hg increase of backpressure, so in theory the stock exhaust on a 200HP IO-360 would cost us 4HP. In practice, I believe stock exhaust systems cost a bit more.

You could replace the full exhaust with some short stacks and gain that power back, but there's still something better. As the exhaust pulses travel through the exhaust, they form areas of pressure in the pipe that are actually lower than ambient. With careful sizing and spacing of the pipes, you can time these low pressure areas to pass by a cylinder just as its exhaust valve opens. That helps to draw the gases out of the cylinder, and wastes less power. Some of these tuned exhausts are appearing on the market, but I haven't seen any exhaust pressure graphs of them yet. The concept is sound, though, and suited for aircraft engines that tend to operate in a narrow RPM range.