Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Nefarious on January 11, 2020, 01:24:30 PM
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On the speed, both Indicated and Ground, for 8th Air Force Bomber Formations.
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"The Wrong Stuff" by Truman Smith mentions that 150mph was the speed for 8th AF B17 formations. Slow enough for all planes to maintain formation.
Haven't found any official stats, yet.
:salute
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Here you go. I searched for "speed of B-17 bomber formation."
150 indicated and ground speed would depend on altitude.
https://www.thevintagenews.com/2016/03/12/b-17-fly-formation-via-b-17-pilot-training-manual-not-flown-closer-one-another-50-feet-nose-tail/
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I do not know how true the film info is, but Target for Today mentioned group climb as 150mph, 100ft/min and later after bombing, lead straight for 15 sec, then turn to rally point, speed 155 ias, making s turns for others to catch up.
Memphis Belle mentioned climb 300ft/min after 10000ft.
How to Fly the Boeing B-17 "Flying Fortress" - Flight Procedures (Restored 1943) mentiones speed 150 ias and power used for normal cruise is depending on flight conditions- desired range, fuel available, weather conditions, altitude, gross weight etc. Pilot`s operating handbook should have graphical tabels to find performance data and power settings. Like distance travelled to reach target altitude at certain gross weight etc.
Ground speed depends on wind as well.
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Good point about wind but that's an arena setting and will probably be off.
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AH B17 formations can fly at ridiculous speed rendering Bf110, Bf410 useless against bombers if you do not HO them in AH.
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150 mph TAS at 25,000 was typical for flight planning 8th AF ops. B-24 was faster but settled for typical 22,000 feet at 180mph TAS.
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Are we sure these numbers are right?
150TAS at 25K seems kinda slow as that would be somewhere around 100IAS.
150IAS would be somewhere around 225TAS which seems more reasonable to me.
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Are we sure these numbers are right?
150TAS at 25K seems kinda slow as that would be somewhere around 100IAS.
150IAS would be somewhere around 225TAS which seems more reasonable to me.
As FLS posted and hazmatt it is 150 IAS!
TAS is your ground speed which will be higher than your IAS the higher you get in less dense air......
Hope this helps
TC
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As FLS posted and hazmatt it is 150 IAS!
TAS is your ground speed which will be higher than your IAS the higher you get in less dense air......
Hope this helps
TC
TAS only equals ground speed in still air.
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TAS only equals ground speed in still air.
I disagree.....
True Air Speed
Indicated Air Speed
One is corrected, one is not....regardless of atmospheric conditions
Then again I do suffer dementia/memory loss
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What do pilots use IAS for? (it is a 1 word answer)
What do pilots and others use TAS for? (has several answers)
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What do pilots use IAS for? (it is a 1 word answer)
What do pilots and others use TAS for? (has several answers)
Well, I was a professional pilot for 41 years - 37 in an airline so let me try to offer a few answers.
Pilots use IAS for;
1: V1
2: Vr
3: V2
4: Flap retract and extend speeds
5: Gear extend speeds
6: Rudder travel limit speeds
7: Airspeed limits such as 200KIAS when <3000 ft AGL and 10 miles from an airport + 250 KIAS below 10,000 ft.
8: Best Rate and best angle climb speeds
9: Airframe Limit speed
10: Turbulent air penetration speed
I could go on
TAS of course, is used as a flight planning tool so when compared with predicted winds, the pilot can accurately estimate his enroute time and thereby accurately estimate the amount of fuel that will be required for a flight. Unless I am missing what you are trying to say, I am sure that you can appreciate that a jet flying west at 450 KTAS but encountering a 100 knot headwind will only have a groundspeed of 350 knots.
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Well, I was a professional pilot for 41 years - 37 in an airline so let me try to offer a few answers.
Pilots use IAS for;
1: V1
2: Vr
3: V2
4: Flap retract and extend speeds
5: Gear extend speeds
6: Rudder travel limit speeds
7: Airspeed limits such as 200KIAS when <3000 ft AGL and 10 miles from an airport + 250 KIAS below 10,000 ft.
8: Best Rate and best angle climb speeds
9: Airframe Limit speed
10: Turbulent air penetration speed
I could go on
TAS of course, is used as a flight planning tool so when compared with predicted winds, the pilot can accurately estimate his enroute time and thereby accurately estimate the amount of fuel that will be required for a flight. Unless I am missing what you are trying to say, I am sure that you can appreciate that a jet flying west at 450 KTAS but encountering a 100 knot headwind will only have a groundspeed of 350 knots.
I was simplifying it.... Your 1 thru 10 for KIAS (knots indicated) I put it with 1 word as. Manuevering
Agree with you on KTAS.... Plane performance stats, flight plan, etc
But if you're running into a head wind of 100 knots would that not show up on your TAS indicator as 350 because of the drag it is putting on the airframe?
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But if you're running into a head wind of 100 knots would that not show up on your TAS indicator as 350 because of the drag it is putting on the airframe?
No. Your ground speed would significantly change, but your TAS - the speed you're actually moving through the air mass - would not change.
There's an exception, as always, and that's if there's wind shear, but typically you only encounter that at very low levels.
- oldman
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I guess I've lost the use of more gray matter than I thought, because the physics are not adding up in my brain to see that, LOL
Edit: initially yes! If your TAS hits a head wind of a 100 knots, for a little bit the plane will be able to push forward at a rate of 450 KTAS, but it will slow down depending how long the plane continues to fly into the head wind..... I can not see the "TAS Indicator" continue to say 450 knots when in reality the 100 knot head wind (drag) has slowed it down to 350 knots.... <---- that is your TAS(corrected)
Explain to me what I'm missing, I can not see the gauge saying the plane is doing 450 KTAS, when it is not....how does that help the pilot in any way giving a false reading saying that your doing 450, but you're actually a 100 knots slower
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I guess I've lost the use of more gray matter than I thought, because the physics are not adding up in my brain to see that, LOL
Edit: initially yes! If your TAS hits a head wind of a 100 knots, for a little bit the plane will be able to push forward at a rate of 450 KTAS, but it will slow down depending how long the plane continues to fly into the head wind..... I can not see the "TAS Indicator" continue to say 450 knots when in reality the 100 knot head wind (drag) has slowed it down to 350 knots.... <---- that is your TAS(corrected)
Explain to me what I'm missing
Best explanation I ever read was in Langewiesche's "Stick and Rudder." He likened a plane moving through an air mass to a man walking through a train car. Regardless of how fast the train is moving across the landscape, the relative motion of the man within the car was the same.
- oldman
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To add, if we are talking modern fighter jets..... Lets say starting back with the F4 phantom II (one that I'm very familiar with and have done high-powered turn qualifications in among other jets)
Then they have the thrust-to-weight ratio to overcome head winds, or the F-15 etc....
If we are talking prop planes and/or passenger jets, they don't have the ability
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Best explanation I ever read was in Langewiesche's "Stick and Rudder." He likened a plane moving through an air mass to a man walking through a train car. Regardless of how fast the train is moving across the landscape, the relative motion of the man within the car was the same.
- oldman
I actually have that old book in my collection but haven't opened it in over 30 years, heh
I understand what you're saying there, but in a plane or jet, you are strapped in.....like a stationary part of the cockpit
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"but in a plane or jet, you are strapped in.....like a stationary part of the cockpit"
physics doesn't care if your strapped in to the cockpit or riding free in the hold.it works the same.
its why you can throw a ball from one hand to the other while riding in an airplane(car,train) without the ball immediately bouncing off the rear bulkhead.
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Let me get this straight - TAS takes into account of your altitude in addition to your IAS? Same speedo dial as it does in Aces High?
Ground speed would only be available through GPS or through radar navigation systems?
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Let me get this straight - TAS takes into account of your altitude in addition to your IAS? Same speedo dial as it does in Aces High?
Ground speed would only be available through GPS or through radar navigation systems?
Correct. IAS becomes less reliable as an airplane climbs due to air density. Private pilots are taught very early in their training, how to covert IAS to TAS based on altitude and temperature.
And ground speed can also be displayed by DME (distance measuring equipment) used by airplanes not GPS equipped. ATC can also provide groundspeed in a radar environment on pilot request.
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Ok, let's say I'm at 20,000 feet flying west at an indicated airspeed of 100 mph. According to a little conversion calculator I found, my true airspeed is 154 mph. This can vary depending on air temperature. But this mean that I am actually traveling through the air at 154 mph. If there is no wind, then my ground speed is 154 mph. If the wind is blowing west to east at 10 mph, then I have a 10 mph headwind, and my ground speed will be 144 mph, even though my true airspeed is still 154 mph. I am still traveling through the air at 154 mph, but that air is traveling in the opposite direction at 10 mph, so I lose 10 mph in ground speed.
If the wind is blowing east to west at 10 mph, then I have a 10 mph tailwind, and my ground speed will be 164 mph. I am still traveling through the air at 154 mph, but that air is traveling in the same direction I am, so I gain 10 mph in ground speed.
Now let's say my stall speed is 80 mph. Stall speed is indicated air speed, regardless of my true air speed. The less dense air means that I need more of it to provide the lift I need. So if I slow down to 80 mph indicated air speed, I will stall, even though my true air speed is 123 mph.
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Ok, let's say I'm at 20,000 feet flying west at an indicated airspeed of 100 mph. According to a little conversion calculator I found, my true airspeed is 154 mph. This can vary depending on air temperature. But this mean that I am actually traveling through the air at 154 mph. If there is no wind, then my ground speed is 154 mph. If the wind is blowing west to east at 10 mph, then I have a 10 mph headwind, and my ground speed will be 144 mph, even though my true airspeed is still 154 mph. I am still traveling through the air at 154 mph, but that air is traveling in the opposite direction at 10 mph, so I lose 10 mph in ground speed.
If the wind is blowing east to west at 10 mph, then I have a 10 mph tailwind, and my ground speed will be 164 mph. I am still traveling through the air at 154 mph, but that air is traveling in the same direction I am, so I gain 10 mph in ground speed.
Now let's say my stall speed is 80 mph. Stall speed is indicated air speed, regardless of my true air speed. The less dense air means that I need more of it to provide the lift I need. So if I slow down to 80 mph indicated air speed, I will stall, even though my true air speed is 123 mph.
100% correct.
Only thing I could add is some visualizations. And definition of CAS Calibrated air speed.
IAS is a measure of the pressure change as a result of putting a tube pointed into the wind at speed. So when you go higher, there is less pressure differential do to less atoms going into the tube. In the same way less atoms are striking your wing causing less lift, and hence you will need to fly at a higher AOA to maintain the same lift. Since a give plane stalls at the same critical AOA, your "Stall Speed" will always be the same IAS.
Now since your tube can not always be pointed directly forward as your AOA changes, you will be presenting a cross section of the tube into the air stream. This will cause your Air speed indicator to read slower than if it was pointed directly into the wind. CAS is the IAS adjusted for this error.
HiTech
Aces High does the inverse calculation from CAS (used to determine all forces) to IAS which is only used to display on the gauge.
HiTech
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100% correct.
Only thing I could add is some visualizations. And definition of CAS Calibrated air speed.
HiTech
Yay! I got it right! And thanks for the explanation of CAS. That part always left me a little puzzled.
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Recent example of a major difference between IAS and TAS
https://www.nytimes.com/2020/02/09/world/british-airways-subsonic-flight.html
https://www.bbc.com/news/uk-england-london-51433720
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Recent example of a major difference between IAS and TAS
https://www.nytimes.com/2020/02/09/world/british-airways-subsonic-flight.html
https://www.bbc.com/news/uk-england-london-51433720
Those articles are an example of the difference between TAS and Groundspeed. The Aircraft TAS remains unchanged and relative to their filed Flight Plan speed (somewhere around 490 - 510kts). While they attained a top Groundspeed of 825mph for 24 minutes.
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I guess I've lost the use of more gray matter than I thought, because the physics are not adding up in my brain to see that, LOL
Edit: initially yes! If your TAS hits a head wind of a 100 knots, for a little bit the plane will be able to push forward at a rate of 450 KTAS, but it will slow down depending how long the plane continues to fly into the head wind..... I can not see the "TAS Indicator" continue to say 450 knots when in reality the 100 knot head wind (drag) has slowed it down to 350 knots.... <---- that is your TAS(corrected)
Explain to me what I'm missing, I can not see the gauge saying the plane is doing 450 KTAS, when it is not....how does that help the pilot in any way giving a false reading saying that your doing 450, but you're actually a 100 knots slower
True airspeed isn't an independent or direct airspeed measurement - it is simply indicated airspeed corrected for air density, sometimes just by dialing in the pressure altitude on the instrument itself. Not all aircraft even have a true airspeed gauge, as it isn't a required instrument for flying the aircraft. Indicated airspeed is simply a measurement of static and dynamic pressure at the location of the pitot tube (or whatever actual pressure sensor is used). If you are encountering wind shear or turbulence that makes your indicated airspeed fluctuate, then your true airspeed reading will fluctuate as well. So if the true airspeed indicator reads 450 knots, then that simply means that the pressures (actually the difference in pressures) measured by the pitot tube is such that would be produced by a wind of the set air density passing at a speed of 450 knots. It doesn't matter if the pressure is steady state, or if it caused by a malfunction of the pitot tube (icing, a bug in the inlet, etc). It is simply an indication of the pressures that the instrument is "seeing." There is no logic in the airspeed indicator to determine if the measurement is useful, or even if it is correct.
Mike
Mike
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But what if your plane is on a conveyor belt?
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But what if your plane is on a conveyor belt?
Oh no not again!
Sent from my Moto Z (2) using Tapatalk
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But what if your plane is on a conveyor belt?
OHHHH NOOOOooo you started that AGAIN!!!!!
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So what about German Bombers over Britain circa August 1940? :D
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So what about German Bombers over Britain circa August 1940? :D
I'm guessing max range power setting.
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For WWII planes outside of compressibility, there are generally these three airspeeds that matter.
IAS = indicated airspeed = what is read on the airspeed indicator, which is using a pitot tube to estimate airspeed.
CAS = calibrated airspeed = the airspeed after IAS is corrected for calibration of the airspeed indicator/pilot tube. CAS is usually close to IAS, and I think they might be the same in AH, i.e., the airspeed indicators are modeled to be already calibrated.
TAS = true airspeed = the true speed of the airplane through the air = sqrt(rho0 / rho) * CAS, where rho0 is air density at sea level, and rho is the air density at the altitude you are flying. At high altitudes, TAS is much larger than IAS.
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For WWII planes outside of compressibility, there are generally these three airspeeds that matter.
IAS = indicated airspeed = what is read on the airspeed indicator, which is using a pitot tube to estimate airspeed.
CAS = calibrated airspeed = the airspeed after IAS is corrected for calibration of the airspeed indicator/pilot tube. CAS is usually close to IAS, and I think they might be the same in AH, i.e., the airspeed indicators are modeled to be already calibrated.
TAS = true airspeed = the true speed of the airplane through the air = sqrt(rho0 / rho) * CAS, where rho0 is air density at sea level, and rho is the air density at the altitude you are flying. At high altitudes, TAS is much larger than IAS.
When it comes to "questions" on the "Aces High Forums", I've always have looked at the question as pertaining to Aces High (the game itself).... I guess this is the one "sub-forum" where it can pertain to both the Aces High game and to "Real Life"
CAS = Calibrated Air Speed (CAS = corrected air speed)
Would not both be correct for CAS?
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Mongoose
That handy little converter tool you haappened to have used in your post, didn't happen to be an "asa E6-B Flight Computer" sliderule, would it? just curious....
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thank you HiTech, for help correcting me on my "TAS<-----corrected where I had originally typed it, then you gave the proper TAS = CAS....
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Instead of using these different copys/versions of these asa E6-B calculating/slide rules.... I have a pretty neat one that is computer-based and is very informative....dew point, humidity, air density, wind direction. HDG, TAS, IAS, cross wind angle, etc......
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Mongoose
That handy little converter tool you haappened to have used in your post, didn't happen to be an "asa E6-B Flight Computer" sliderule, would it? just curious....
Not this time. I did a quick internet search for IAS to TAS converter.
I have an E6-B around here somewhere, but it was quicker to do the internet search.
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Heh, I should start using Google or Bing Search more these days, then I wouldn't be disagreeing with other people's correct answers and ,LOL, look smart too.....haha
Edit: decided to give Google and Bing search a go at "TAS, CAS, IAS and their meaning regarding aviation" ....people don't need books anymore in this day and age, do they.....
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150 mph IAS at 25,000 was typical for flight planning 8th AF ops. B-24 was faster but settled for typical 22,000 feet at 180mph TAS.
I corrected TAS to IAS as it should be. TAS over the ground with no wind conditions was typically about 210mph TAS at 25K