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Old 11-19-2018, 03:56 AM   #1
gdotts
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Default speed problem

Flying level...I can't seem to ever catch up to a B-17. I thought P-51 is faster than a B-17???

Flaps not engaged....
Throttle all the way up.....
Prop RPM -Plever all the way up...
WEP seems to do nothing....
What am I doing wrong?

fuel mixture????????

Please advise
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Old 11-19-2018, 04:26 AM   #2
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Quote:
Originally Posted by gdotts View Post
Flying level...I can't seem to ever catch up to a B-17. I thought P-51 is faster than a B-17???



Flaps not engaged....

Throttle all the way up.....

Prop RPM -Plever all the way up...

WEP seems to do nothing....

What am I doing wrong?



fuel mixture????????



Please advise


Need a little more info- what altitude are you at? Is this a created mission or multiplayer? Yes, you should be able to catch the B17 with no issues. Is your mixture set to run? And do you have the carburetor air control handles forward? (That’s the two levers just above the flaps lever on the left)


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Old 11-19-2018, 11:06 AM   #3
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The left carb. control lever (Ram Air) should be to the rear. Forward is Filtered Air for on the ground. To the rear is unfiltered Ram Air, and should only be used in very specific situations during flight, when ice particles might form. See the manual for a description of these conditions.

Beyond this, having a TRK and MIZ might help with determining your issue.
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Old 11-19-2018, 12:53 PM   #4
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Altitude 20,000.... created mission .... Thanks for the help!
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Old 11-19-2018, 12:56 PM   #5
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Maybe the B-17 has unrealistically high speeds set in the waypoint details? What is your IAS?
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Old 11-19-2018, 04:46 PM   #6
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Quote:
Originally Posted by gdotts View Post
Prop RPM -Plever all the way up...
Do you mean max RPM on the propeller?
At high airspeeds, this will slow you down as the relative airflow will drive the propeller, and act as a speed brake. Try setting a max cruise power instead, 2400RPM and 36" Manifold Pressure.

And, since you didn’t mention it, I must ask... You did retract your gear..?
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Old 11-19-2018, 06:27 PM   #7
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make sure that your left side looks like this
https://i.imgur.com/RCZdz2r.jpg
than make sure when you are at 20k ft alti that your high gear of superchargers is engaged next to fule boost switch you have light indicator should be light up.
at 20k ft you shpould be able to maintain max boost which is 67inHg (manifold pressure gage is primary indicator showing the pilot how much power engine is making the second one is RPM gage directly below) you want 67inHg at 3000rpm for max preformance but engine limitation is about 5min for this setting 61inHg/3000rpm 15min
46inHg/2700rpm is max continous power or climb power
you should be able not only to catch up to b-17 you probably could buzz it preaty fast
check your landign gear
check your radator controls switches make sure that they are in automatic position
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Old 11-19-2018, 09:13 PM   #8
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At 20k feet, your ram air filter should be full open as this impedes airflow into the manifold. At those altitudes you should see a 10lb boost in manifold pressure Your prop should be full RPM @ 3000. If your aircraft cant manage 300kts IAS on the dial at that alttitude, then you have something dangling in the airflow and its most likely your flaps.

Also, make sure (VERY IMPORTANT) that your supercharger is kicking in. If you arent above critical altitude, your performance WILL suffer. Critical altitude is that altitude where manifold pressure drops below MSL atmospheric pressure and you arent getting a full charge in the combustion chamber. Thats when the supercharger is supposed to kick in...and that is usually between 14k and 18k altitude. Could be higher depending on weather conditions. One last thing: unless you are flying in cold, humid weather and are anticipating ice, DO NOT OPEN THE CARB HEAT. This redirects exhaust gas into the intake manifold specifically to melt ice in the carburetor throat. This also drops your manifold pressure drastically. DO NOT OPEN THE CARB HEAT.
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Last edited by PingPongChampeen; 11-19-2018 at 09:20 PM.
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Old 11-20-2018, 12:42 AM   #9
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critical altitude is when supercharger cant provide maximum boost anymore it doesnt mean that boost drops below msl atm pressure it means that supercharger for example in v-1650-7 cant provide 67inhg of boost for specyfic altitude.
p-51-d equiped with v-1650-7 critical alt for low supercharger speed is around 8k ft at 67inHg
for 61inHg it will be higher around 10k ft from this point supercharger at low speed in p-51 cant keep 61 inhg boost till 16-18k ft p-51 will loose power than high supercharger speed will be engaged moving critical alt to around 24k or something like this. Ram air intake is using plane velocity to creat boost at high speeds this boost gain is quite good
without ram air critical alt for 61 inHg drops from 10k to 7.5k quite a lot i would say.
below critical alt p-51's engine will suffer proformance due to throttling looses in supercharger system
p-51 will have less power at MLS that at 8k alt at the same boost level.
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Old 11-20-2018, 12:51 AM   #10
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Quote:
Originally Posted by grafspee View Post
critical altitude is when supercharger cant provide maximum boost anymore it doesnt mean that boost drops below msl atm pressure it means that supercharger for example in v-1650-7 cant provide 67inhg of boost for specyfic altitude.
p-51-d equiped with v-1650-7 critical alt for low supercharger speed is around 8k ft at 67inHg
for 61inHg it will be higher around 10k ft from this point supercharger at low speed in p-51 cant keep 61 inhg boost till 16-18k ft p-51 will loose power than high supercharger speed will be engaged moving critical alt to around 24k or something like this. Ram air intake is using plane velocity to creat boost at high speeds this boost gain is quite good
without ram air critical alt for 61 inHg drops from 10k to 7.5k quite a lot i would say.
below critical alt p-51's engine will suffer proformance due to throttling looses in supercharger system
p-51 will have less power at MLS that at 8k alt at the same boost level.
You're right about critical altitude, thats my mistake. Ive had the Mustang up to 40k feet and still have a few lbs boost from the supercharger before stalling. Anyways, the supercharger SHOULD kick in at a specific manifold pressure and specific altitude via a Bellows tube instrument IIRC.
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