'nuther question: highest TAS...

[xerj]

.... for a normally aspirated piston occurs at sea level and full power, but
for a turbonormalised engine it will be at critical altitude, right?

Thanks in advance.

[Jose]

> [highest TAS] for a normally aspirated piston occurs at sea level and full power

In my experience, I get higher TAS at altitude. For a normally
aspirated single, 6-9000 feet or so.

Jose
--
Money: what you need when you run out of brains.
for Email, make the obvious change in the address.

[Mortimer Schnerd, RN]

xerj wrote:
> ... for a normally aspirated piston occurs at sea level and full power, but
> for a turbonormalised engine it will be at critical altitude, right?



If you look at a performance chart, you'll see that the highest true airspeed
for a normally aspirated aircraft is more likely to be around 6000 feet or so.



--
Mortimer Schnerd, RN

[Peter Duniho]

"Jose" > wrote in message
.. .
> In my experience, I get higher TAS at altitude. For a normally aspirated
> single, 6-9000 feet or so.

At cruise power, yes. As far as I know, you get more loss of thrust than of
drag (due to power loss) above sea level, so at full power, TAS always goes
down from sea level (for normally aspirated engines).

Just as xerj says.

[xerj]

> If you look at a performance chart, you'll see that the highest true
> airspeed for a normally aspirated aircraft is more likely to be around
> 6000 feet or so.

Isn't that for something less than full power, i.e. 75%? I'm talking max
power.

Here's a c'n'p from this page:
http://www.nar-associates.com/technical-flying/altitude/part1/altpart1.html

"The right hand intersection of the curves gives the maximum velocity in
level flight at that altitude. First, notice that for a normally aspirated
piston engine the maximum velocity in level flight occurs at sea level."

[Ron Rosenfeld]

On Tue, 18 Oct 2005 23:29:51 GMT, "Mortimer Schnerd, RN"
> wrote:

>If you look at a performance chart, you'll see that the highest true airspeed
>for a normally aspirated aircraft is more likely to be around 6000 feet or so.

Not at full power.

If I look at charts that show a full throttle curve, what I see is that TAS
increases up to the maximum altitude that any particular power setting can
be achieved; after that it falls.

Full power can only be achieved at sea level.

At least for a Mooney Ovation 2, for which I happen to have available that
type of curve, it is very clear that maximum TAS is achieved at maximum
power at SL (about 193KTAS)

For 75% power, maximum TAS is achieved at 8000', which is the maximum
altitude that one can obtain 75% power (about 190KTAS).


Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

[George Patterson]

Ron Rosenfeld wrote:

> Full power can only be achieved at sea level.

But you can do better than that at places that are below sea level. As long as
they aren't actually under water, that is. :-)

George Patterson
Drink is the curse of the land. It makes you quarrel with your neighbor.
It makes you shoot at your landlord. And it makes you miss him.

[BTIZ]

"George Patterson" > wrote in message
news:Pyh5f.2738$fC3.2250@trndny01...
> Ron Rosenfeld wrote:
>
>> Full power can only be achieved at sea level.
>
> But you can do better than that at places that are below sea level. As
> long as they aren't actually under water, that is. :-)
>
> George Patterson

Been there George.... Death Valley in the cold of winter..
BT

[Ron Rosenfeld]

On Wed, 19 Oct 2005 01:45:19 GMT, George Patterson >
wrote:

>Ron Rosenfeld wrote:
>
>> Full power can only be achieved at sea level.
>
>But you can do better than that at places that are below sea level. As long as
>they aren't actually under water, that is. :-)
>
>George Patterson
> Drink is the curse of the land. It makes you quarrel with your neighbor.
> It makes you shoot at your landlord. And it makes you miss him.





Well sure, depending on the temperature.

You can also achieve the same result at or above sea level with colder than
standard temperature conditions.

But in my response, I did not consider that a very detailed discussion of
the effects of temperature, humidity and altitude on engine performance was
going to add much, given the original question.

Do you know if the OP's supposition that the highest TAS of a turbo'd a/c
is at the critical altitude is correct?




Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

[Marc J. Zeitlin]

Ron Rosenfeld wrote:

> Do you know if the OP's supposition that the highest TAS of a turbo'd
> a/c
> is at the critical altitude is correct?

The highest TAS of a propeller driven aircraft will occur at the highest
altitude at which the power being developed can occur. In other words,
if you want to fly at 65% power, fly at the highest altitude at which
65% power can be developed.

--
Marc J. Zeitlin
http://www.cozybuilders.org/
Copyright (c) 2005

[Mortimer Schnerd, RN]

xerj wrote:
>> If you look at a performance chart, you'll see that the highest true
>> airspeed for a normally aspirated aircraft is more likely to be around
>> 6000 feet or so.
>
> Isn't that for something less than full power, i.e. 75%? I'm talking max
> power.


Well, maybe so. My performance charts list speeds for 55%, 65% and 75% power
only. The only time I fly at full throttle and more than 75% is on takeoff, and
that's not a speed run... that's time to reach for the sky instead. Once I
level off, I'll throttle back to 75% as a maximum... conducive to long engine
life, etc. If the manufacturers had intended me to fly at 100% power, they'd
include a performance chart for that setting.

Of course, as I climb, full throttle yields less and less, unless I'm in a
turbocharged aircraft. Even then, it runs out of oomph at some point.



--
Mortimer Schnerd, RN

[Ron Rosenfeld]

On Wed, 19 Oct 2005 03:03:30 GMT, "Marc J. Zeitlin"
> wrote:

>The highest TAS of a propeller driven aircraft will occur at the highest
>altitude at which the power being developed can occur. In other words,
>if you want to fly at 65% power, fly at the highest altitude at which
>65% power can be developed.

That does make intuitive sense.


Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

[xerj]

> The highest TAS of a propeller driven aircraft will occur at the highest
> altitude at which the power being developed can occur. In other words, if
> you want to fly at 65% power, fly at the highest altitude at which 65%
> power can be developed.

That makes sense.

I actually found an article I'd forgotten about, about turbonormalization at
the website I'd linked to earlier which shows it with power curves and other
charts.

http://www.nar-associates.com/technical-flying/turbo/turbo.pdf