Figuring out what affects my speed

[Mxsmanic]

This morning I'm flying my sim Baron 58 towards KVYS, and I notice
that my airspeed is about 217 kts, much higher than usual. I'm level
at 5000 feet MSL, altimeter is 3038, clear weather, throttles full,
mixture set for peak EGT roughly, props set to 2520 RPM, about 150 RPM
below redline. The temperature outside is -1° C.

The mystery for me is that 217 kts (slightly in the yellow arc) is
unusually fast. I'm not sure what I'm doing different. Usually I'm
just below the yellow arc in cruise at this range of altitudes.

So throttle, mixture, prop, and altitude can surely affect IAS in
level flight, but what else? How much does the gradual burning of
fuel make a difference? Would it boost my speed by 20 kts or more as
it burns off? I started out with almost a full load of fuel, and now
about half of it is gone.

I'm just trying to figure out what factors I may be overlooking.

--
Transpose mxsmanic and gmail to reach me by e-mail.

[Steve Foley]

"Mxsmanic" > wrote in message
...
> This morning I'm flying my sim Baron 58 towards KVYS, and I notice
> that my airspeed is about 217 kts,

Indicated, calibrated, or true?

[Mxsmanic]

Steve Foley writes:

> Indicated, calibrated, or true?

TAS. Indicated is about 195. Speed over the ground is about 220,
although I don't consider that a factor here.

In most cases I see somewhat lower speeds in cruise. I'm trying to
figure out what I did different this time (or what might be different
about conditions) that would produce a noticeably higher speed.

--
Transpose mxsmanic and gmail to reach me by e-mail.

[ktbr]

Mxsmanic wrote:
> In most cases I see somewhat lower speeds in cruise. I'm trying to
> figure out what I did different this time (or what might be different
> about conditions) that would produce a noticeably higher speed.
>

You don't say what the air temp is. But anyway, this is all
academic in terms of a simulator, but there any number of
things that can affect the airplanes actual (TRUE) airspeed:

Weight
CG (loading)
air density (temp/pressure)
power (RPM)
propeller efficiency
how slick is the fuselage/wings? (parasitic drag?)

Through various combinations of these an airplanes max
true airspeed can vary considerably from ;book/ values.

[Viperdoc[_4_]]

Just for the record, a real Baron will not see 195 true, and most operators
do not cruise at 2520 rpm and egt peak. The fuel burn is high under these
conditions, and it is also loud inside.

These operating conditions are probably not within the normal operating
parameters of either the POH or the suggestions by John Deakin, whomever you
chose to believe.

Most pilots will cruise at more reduced power settings to keep the fuel burn
down if nothing else.

[Thomas Borchert]

Viperdoc,

> These operating conditions are probably not within the normal operating
> parameters of either the POH or the suggestions by John Deakin, whomever you
> chose to believe.
>

He's been told numerous times to read the POH and Deakin. He doesn't. Yet he
claims he wants to learn all he can. He's a liar.

--
Thomas Borchert (EDDH)

[Thomas Borchert]

Ktbr,

> . But anyway, this is all
> academic in terms of a simulator,
>

Hey, maybe he finally washed the bugs off.

--
Thomas Borchert (EDDH)

[Rick[_1_]]

Thomas Borchert wrote in message ...
>Ktbr,
>
>> . But anyway, this is all
>> academic in terms of a simulator,
>>
>
>Hey, maybe he finally washed the bugs off.

Windex on my monitor always gets me a few extra knots.

- Rick

[Mxsmanic]

ktbr writes:

> You don't say what the air temp is.

It was -1° C at 5000 feet.

> But anyway, this is all
> academic in terms of a simulator, but there any number of
> things that can affect the airplanes actual (TRUE) airspeed:
>
> Weight
> CG (loading)
> air density (temp/pressure)
> power (RPM)
> propeller efficiency
> how slick is the fuselage/wings? (parasitic drag?)
>
> Through various combinations of these an airplanes max
> true airspeed can vary considerably from ;book/ values.

I've been thinking and two possibilities come to mind: cowl flaps
closed, and prop speed reduced. I didn't think that cowl flaps made
much difference on a Baron, certainly not 20-30 kts, but maybe. I
also thought that reducing the prop speed might have something to do
with it. The aircraft slows down initially when I reduce the prop
speed, but up to now I haven't watched it over time to see if it ends
up moving faster, so I might try that.

--
Transpose mxsmanic and gmail to reach me by e-mail.

[Mxsmanic]

Viperdoc writes:

> Just for the record, a real Baron will not see 195 true ...

What is your source of information? The manual says 223 indicated, so
it must be able to achive at least that in true airspeed.

> ... and most operators
> do not cruise at 2520 rpm and egt peak. The fuel burn is high under these
> conditions, and it is also loud inside.

Fortunately, I don't have to pay for fuel, so economy is not an issue.
I've only recently started to adjust mixture and prop settings, and
I'm still not clear how they are supposed to interact. I'm thinking
that some adjustment I made increased the speed of the aircraft.

--
Transpose mxsmanic and gmail to reach me by e-mail.

[Paul kgyy]

Probably the temperature. At 25" MP and 2520 rpm, I'd guess you would
be running about 78% power under standard temperature conditions
(15C?). But at -1C the denser air is giving you additional power
output so you're probably closer to 80%. This is harder than most of
us would be willing to run at 5000 ft. Peak EGT at this power setting
is also asking for engine detonation.

[Mxsmanic]

Paul kgyy writes:

> Probably the temperature. At 25" MP and 2520 rpm, I'd guess you would
> be running about 78% power under standard temperature conditions
> (15C?). But at -1C the denser air is giving you additional power
> output so you're probably closer to 80%.

OK. That sounds like enough to account for the difference in speed
(?).

> This is harder than most of us would be willing to run at 5000 ft.

My virtual funds are unlimited, but in real life, with a limited
budget, I'd be far more conservative.

> Peak EGT at this power setting is also asking for engine detonation.

I haven't noticed anything, but I don't know if this is simulated (and
I'm not even sure that it occurs to a significant degree, as there
seems to be a lot of disagreement on that).

--
Transpose mxsmanic and gmail to reach me by e-mail.

[Paul kgyy]

Mxsmanic wrote:
> Paul kgyy writes:
>
> > Probably the temperature. At 25" MP and 2520 rpm, I'd guess you would
> > be running about 78% power under standard temperature conditions
> > (15C?). But at -1C the denser air is giving you additional power
> > output so you're probably closer to 80%.
>
> OK. That sounds like enough to account for the difference in speed
> (?).

The power chart in your POH should tell you how to adjust the manifold
pressure for nonstandard temperature conditions.

[Peter Dohm]

> Probably the temperature. At 25" MP and 2520 rpm, I'd guess you would
> be running about 78% power under standard temperature conditions
> (15C?). But at -1C the denser air is giving you additional power
> output so you're probably closer to 80%. This is harder than most of
> us would be willing to run at 5000 ft. Peak EGT at this power setting
> is also asking for engine detonation.
>
I might have to read ordinary threads while his sim is getting new
cylinders.

Peter

[Thomas Borchert]

Paul,

> under standard temperature conditions
> (15C?).
>

5 C, actually. 15 is standard on the ground. You lose 2 per 1000 feet
in a standard atmosphere.

--
Thomas Borchert (EDDH)

[ktbr]

Peter Dohm wrote:
> I might have to read ordinary threads while his sim is getting new
> cylinders.
>
Hopefully the motherboard is still under warranty.

[Mxsmanic]

Paul kgyy writes:

> The power chart in your POH should tell you how to adjust the manifold
> pressure for nonstandard temperature conditions.

It says maximum cruise power at 20° rich of peak, 25" MP, 2500 RPM,
for minus 20 degrees OAT, with the best listed performance at 6000
feet (approximately 200 KTAS), although I'm at 5000 feet because I'm
IFR and that's not on the chart. That's about what I'm getting now
(211 KTAS with the same settings, as close as I can get them).
Economy cruise is about 40 kts slower, but I have virtual cash to
burn.

The cold air doesn't help performance, according to the POH chart.
Maybe it's the adjustments I'm making; I've only recently started
adjusting mixture and prop myself (I used to let the sim do it).

--
Transpose mxsmanic and gmail to reach me by e-mail.

[george]

Peter Dohm wrote:

> > Probably the temperature. At 25" MP and 2520 rpm, I'd guess you would
> > be running about 78% power under standard temperature conditions
> > (15C?). But at -1C the denser air is giving you additional power
> > output so you're probably closer to 80%. This is harder than most of
> > us would be willing to run at 5000 ft. Peak EGT at this power setting
> > is also asking for engine detonation.
> >
> I might have to read ordinary threads while his sim is getting new
> cylinders.
>
He must have gotten his monitor onto the step :-)

[[email protected]]

george wrote:
> >
> He must have gotten his monitor onto the step :-)

George, you really made me smile with that comment :-) Extremely
clever, inside pilot joke... and not mean.

Thanks!
Kev

[Duncan (NZ)]

In article >,
says...
> This morning I'm flying my sim Baron 58 towards KVYS, and I notice
> that my airspeed is about 217 kts, much higher than usual. I'm level
> at 5000 feet MSL, altimeter is 3038, clear weather, throttles full,
> mixture set for peak EGT roughly, props set to 2520 RPM, about 150 RPM
> below redline. The temperature outside is -1° C.
>
> The mystery for me is that 217 kts (slightly in the yellow arc) is
> unusually fast. I'm not sure what I'm doing different. Usually I'm
> just below the yellow arc in cruise at this range of altitudes.
>
> So throttle, mixture, prop, and altitude can surely affect IAS in
> level flight, but what else? How much does the gradual burning of
> fuel make a difference? Would it boost my speed by 20 kts or more as
> it burns off? I started out with almost a full load of fuel, and now
> about half of it is gone.
>
> I'm just trying to figure out what factors I may be overlooking.

Temperature *and* pressure (ie what's the QNH?).

Other obvious factors, loading (including fuel).

--
Duncan

[Mxsmanic]

Duncan writes:

> Temperature *and* pressure (ie what's the QNH?).

It was variable, being high in some spots and low in others along the
route. I couldn't tell if anything changed significantly as the
altimeter changed.

I will try some flights in warmer and clearer weather and see if I see
the same thing.

--
Transpose mxsmanic and gmail to reach me by e-mail.

[Duncan (NZ)]

In article >,
says...
> Duncan writes:
>
> > Temperature *and* pressure (ie what's the QNH?).
>
> It was variable, being high in some spots and low in others along the
> route. I couldn't tell if anything changed significantly as the
> altimeter changed.
>
> I will try some flights in warmer and clearer weather and see if I see
> the same thing.

The guts of it is: cold day and high pressure - you're getting a lot
more oxygen into the cylinders - vs a hot day and low pressue.

While the QNH along the route is variable, it generally doesn't vary
*much* - ie you get to another 'area' and it's an hectopascal or two up
or down. Presumably you were flying with a high QNH (well above STP
value which is 1013 hectopascals at 0' AMSL (1013.2 to be precise,
IIRC)).

--
Duncan

[Paul kgyy]

>
> The guts of it is: cold day and high pressure - you're getting a lot
> more oxygen into the cylinders - vs a hot day and low pressue.
>
> While the QNH along the route is variable, it generally doesn't vary
> *much* - ie you get to another 'area' and it's an hectopascal or two up
> or down. Presumably you were flying with a high QNH (well above STP
> value which is 1013 hectopascals at 0' AMSL (1013.2 to be precise,
> IIRC)).
>
> --
> Duncan

On the other hand, cold high pressure is usually descending air, so the
aircraft is sort of swimming upstream just to stay level.