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AOA, Can someone explain this to me?
- Thread starter Purdue
- Start date
Yeah, but I was thinking about the lighted indicator up on the dash and not the actual AOA on the panel. I don't think gear matters for that, or for the original post for that matter. I think, as A4's said, it's simply a matter of which is better, M/E or M/R, and where.
I am not an AERO expert, and I would agree that into a head wind that is greater than TAS, you will go backward unless you up the power, but if you turn around and use that tail wind, you will go farther if you fly max range as opposed to any other airspeed.
As far as the original poster is concerned, go find Capt. Looby or Capt. Pierce. They will set you straight. Tell them "Donk" (Not me) sent ya.
Do these calculations take into effect the steady decrease in TAS (assuming constant IAS) with decrease in altitude when you're gliding?
Actually, as the speed of the tailwind increases you will keep going colser and closer to max endurance AOA. Nifty, huh? The small gain in airspeed you would get from max range will eventually get negated by the tailwind because it would be more valuable to spend that time aloft basking in said tailwind.
For a prop, max range aoa is L/Dmax aoa (API aero book, among others). That (AOA) doesn't change. To achieve that AOA at a higher altitude, you have to go faster (so TAS will change). That said, the API book also notes that, "since angle of attack indicators are far less precise than airspeed indicators, pilots will usually fly an airspeed that corresponds to L/Dmax AOA." That's probably why they told us 125. Sounds like the IP is in the right ball park but maybe a little off on some of it. It could have something to do with a T-37 left over and the whole difference between jets and props. I use to see a lot of that with IP's that had recently transitioned to the texan from the tweet, but that's just a guess. Hope this helps. As far as being called out in front of the class goes I say just let it go, but if you can't then dig out your aero book and try and respectfully discuss it with the instructor would be my advice.
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The greater the M/R ... the farther I can get. The greater the M/E ... the longer I can stay in the air ... the two are not the same (obviously).
Isn't that why P-3's shut down one while on patrol???To maximize S/E ??? But we would NOT do that with a 747 @ 39,000 feet ... even if told to HOLD .... 'cause you couldn't maintain altitude without all engines and thus M/R and would very soon be converted to M/E and a drift-down (@ max glide speed in this case = M/E) to an altitude you could hold .... and then back to M/R airspeed for that altitude.
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Yes P3s shut down engines (we will shut down two) for M/E purposes at low altitudes. For M/E for times sake it was better to climb as high as four engine will hold you and throttle back as much as possible. Its a tradeoff of the Propeller being very efficient at low altitudes, but the turbine driving them is very efficient at high altititudes.
I personally never liked shuting engines down, did it all the time, but having a bad restart onstation can really ruin your day. I figured the tax payers could afford a little extra gas. Then there is the story how my fe accidently shut down two engines on the same side at night at 1000 ft. He did a great job getting them back on line so it was a non-event except that I didn't need any coffee for the rest of the flight...
I don’t need to tell A4s this as he drives 747 with auto throttle, but for the newbies:
For M/R a parabola is the most efficient. P3s simplified it by periodically stepping up altitudes at 2k steps. Basically you set airspeed and altitude and when you've burned off enough gas you stepped up to the next altitude. It has been too long for me to remember the exact numbers. The rule of thumb was it took 50% of the any extra fuel to carry it to the point where you actually needed it. e.g. If you add an extra 10,000lbs of fuel only 5,000lbs will be used to increase your range. The other 5000lbs is used to carry the extra weight.
My guess is that the AOA indicator used by the AF is not calibrated for accurate use at high altitude cruise conditions. I've seen AOA systems that actually use pressure differential above and below the wing to guess the actual AOA, but I doubt the AF uses them.
Test questions for the Military and FAA are best memorized. Don't overly burden yourself with looking for a deep understanding. Usually the real physics or aerodynamics is overly simplified to the point they lose any valid theoretical meaning.
Really, so why does the Navy use it for precise "speed" control behind the boat? I don't recall airspeed indicator as being part of the pilot's scan while on the ball. In the airliner I fly we don't have any visual indication of AOA (I don't know one that does) but the stall warning and wind shear warning systems sense AOA. So, in escape maneuvers from near CFIT or wind sheer, we basically push the power up, and then pull the nose up until just before you get a stall warning. Sometimes you are into the stick shaker. That is our best indication of L/D max and to hell with the indicated airspeed. I have seen my 140,000+ aircraft dip to indicated speeds of less then 100 knots in wind shear maneuvers and she is still climbing. The deck angle is pretty impressive for a plane that large.
Gator - I think we're talking about two different things, when I was talking about the gear down I was referring to the indicator on the dash. I think you're talking about the actual gauge in the panel, which works all the time. Either way, that doesn't really help him much since he's in the T-6 (and I have no clue what is in that aircraft).
Thinking about all of this makes me glad I decided against majoring in aero engineering.
Thinking about all of this makes me glad I decided against majoring in aero engineering.
Yup, I"m talking about the gauge (which I find far more accurate/useful than the chevrons). Just putting it out there for those that were wondering. I'd have to dig up a pic of a T-6 cockpit, but I'd guess they have the same thing since they don't have a HUD to read out Alpha or a bracket to put the little spermy in.
Bottom line .... you use AOA to land on the BOAT.
In addition: I ALWAYS used AOA in an "at altitude" tactical situation --- a very handy reference in a max-performance maneuver against another air-to-air opponent ..... or doing max-performance turns and loading the plane up at speed .... or when rolling up over the "top" onto your back for a dive bomb roll-in point .... and even when getting really, really slow in a horizontal scissors .
But close to the ground ... ??? I ALWAYS used airspeed and nose attitude (and to a lesser degree, the altimeter/other visual cues) ... as I could follow the AOA guage right into the ground ...
In addition: I ALWAYS used AOA in an "at altitude" tactical situation --- a very handy reference in a max-performance maneuver against another air-to-air opponent ..... or doing max-performance turns and loading the plane up at speed .... or when rolling up over the "top" onto your back for a dive bomb roll-in point .... and even when getting really, really slow in a horizontal scissors .
But close to the ground ... ??? I ALWAYS used airspeed and nose attitude (and to a lesser degree, the altimeter/other visual cues) ... as I could follow the AOA guage right into the ground ...
But that is only max range through the airmass, not on the ground. And I am interested in moving across the ground.
The aero book (and T-34 NATOPS) is just making the "solution" a little easier to grasp and use. Practically speaking, the max range AOA will usually be just fine. But if you want to split hairs (as it seems the IP mentioned wanted to) it isn't entirely accurate.