Aces High Bulletin Board
General Forums => Aces High General Discussion => Topic started by: Gtoraii on September 06, 2001, 05:36:00 PM
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Guys
Ok bone head question, but why both throttle and RPM adjustments? Why would you want to change the RPM?
Would lowering the RPM help with landing? Like more drag from the prop to slow you down?
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Actually just the opposite. The RPM is RPM at the prop not at the engine. By adjusting throttle back you should be able to a) get better gas mileage b) feather the prop all the way or almost all the way depending on the plane when you have a dead engine so that you can have less drag and better glide :)
S!
Rocket
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I have a Wingman twist-stick plus CH Pro Pedals/Throttle combo. My twisty stick throttle is mapped to RPM.
It definitely helps with the fuel economy, definitely provides less thrust landing, I'm of the opinion in doesn't help at all feathering for low drag though.
The only issue is that from time to time I drop the RPM for a landing, only to forget to whip it up again on takeoff. The other night I was fighting a spit and an LA7 in a dora, didn't realize til after the fight I had been flying with minimal RPM (still got em both tho) :)
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RPM control is about fuel economy. You should get slightly better range at lower RPM settings. Otherwise, max RPM will produce max thrust for takeoff and combat. (You should use flaps for slowing to land, and have RPM set max in case you need to abort the landing.)
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The two rotaries on the X-36 throttle are great for RPM adjustment.
I have them mapped for both engines in the P-38L
Great for fuel economy.
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I did some tests and you don't get a fuel economy improvement from reducing RPM. What helps fuel economy is flying slow. The most efficient way to fly slow (in Aces High) is to reduce your throttle. Don't mess with the RPM if you are looking for the best fuel efficiency.
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Funked....
Do more tests :)
Rpm absolutely yields greater fuel economy, especially in combination with reduced manifold pressure.
This is in the pony of course...I can't comment on any other planes.
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Rude can you give me a couple of settings for your aircraft? All the tests I have done show that if you fly two aircraft at a given airspeed and altitude, and one guy uses full RPM while the other guy uses reduced RPM, the full RPM guy gets significantly better specific range (miles per gallon).
Most of the guys who have claimed that reduced RPMs helps were comparing apples to oranges - planes flying at different airspeed. You can almost always get some increase in specific range by reducing airspeed, within certain limits. If somebody can show me a case where reduced RPM will give you better specific range than full RPM at the same airspeed, I will eat my hat. :)
[ 09-07-2001: Message edited by: funkedup ]
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just guessing, but it seems that the propulsion generated by the propellor results (at least directly) from the normal force of the blade surface opposing the force of resistance caused by the density of the air molecules pushing back with their normal force right?
the propellor turns because of the force applied by the engine, which from the blade pov is, we can say, essentially verticle. the more this force is applied to the blade, the more the normal force of the blade has to push to find equallibrium against the air(since the blade is at an angle this would be pronounced), contingent on the density of the air. so the faster the turn, the more the push, the faster the plane goes? (minus the other effects like drag and gravity etc)
so wouldn't less rpm typically result in less air displaced and thus, less push and less rate?
the only measure i can think of where rpm reduction could mean increased fuel economy is at low altitude or in situations where not as much thrust was required to reach the desired speed.
with denser air, the blades wouldn't have to turn as much to produce the same force. so conceivably - if you picked a reasonable cruising speed you might be able to maintain it wih less rpm. of course going to max rpm would result in better performance at any altitude by that standard i would think.
i wish i knew more about airplanes systems and dynamics particular to airplanes to understand the difference better, but from a simple force diagram standpoint alone it doesn't seem like it would help except at low alt and only then if you were happy cruising at less than the max obtainable speed. maybe someone can set me straight :)
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Im glad this thread was started. This is something Iv been wondering myself.
I think we need to know exactly whats happening with RPM and Manifold Pressures.
Whats Truely Changed with Throttle and RPM Settings?
It seems these are generic settings, because differnt planes use differnt systems.
Does a lower RPM setting increase or Decrease the Pitch of the Prop?
Iv got an mechanical background and know my way around engines pretty well and Im lost on this, Its got to be confusing to most.
Id appreciate a clarification on how this system works. It would be great if Staff could answer how this works.
Thanks :D
[ 09-08-2001: Message edited by: Grimm ]
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After doing a little homework I found a couple of articles that explain things fairly well
On Manifold Pressure http://www.avweb.com/articles/pelperch/pelp0015.html (http://www.avweb.com/articles/pelperch/pelp0015.html)
On RPM Settings http://www.avweb.com/articles/pelperch/pelp0016.html (http://www.avweb.com/articles/pelperch/pelp0016.html)
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fish, its like the overdrive in a car. You can cruise at the same speed as with a lower gear, but engine rpm will be slower (reducing friction losses), and volumetric efficiency will be higher with the OD.
At least, thats how it should work. From the tests I've done it looks like fuel consumption in AH is purely a function of manifold pressure.