Hello, how does it work?
How do pilots determine what their TAS in the air will be as the way I understand it, TAS reflects your ETA. Now the wind speed being added or subtracted to the TAS is pretty simple. I just want to know, when a dispatcher or when a pilot plans to fly somewhere, how will he determine TAS - is there any appropriate conversion?
KTAS
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Just take your Mileage and divide it by your TAS.
That will give you a general idea of the time it will take for said trip. Just take the winds into consideration -/+ on top of that for time.
example for a quick idea.
280TAS
340 N/M trip
10 Knots tail wind.
G/S will be appraximately 290.
So 340 / 290 = 1.17 * 60(min) = 70 minutes.
That is just a quick way that I use, usually within +/- 0 minutes.
That will give you a general idea of the time it will take for said trip. Just take the winds into consideration -/+ on top of that for time.
example for a quick idea.
280TAS
340 N/M trip
10 Knots tail wind.
G/S will be appraximately 290.
So 340 / 290 = 1.17 * 60(min) = 70 minutes.
That is just a quick way that I use, usually within +/- 0 minutes.
sorry my wording was wrong, yeah, TAS is the base for the addition or subtraction of the wind for ground speed. This however depends on the winds direction hitting the aircraft
And Thanks !
And Thanks !
Last edited by Front. on Wed Jun 21, 2006 2:32 pm, edited 1 time in total.
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justplanecrazy
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Unless i am going to have to have a talk with our CFI regarding the training they provide...
For the first few flights in the new airplane you might want to use the AFM for your TAS. After that, once you fly the aircraft a few times you get to know what the TAS is going to be at specific altitudes, especially when u do the same damn run for days on end. You subtract or add a few kts depending on what altitude you are cruising at vs. where u normally cruise (TAS will be higher in the winter vs. summer). Plus you have the +/- 5% rule that will help out if your off a little bit.
Its kinda hard to pull out the manual everytime for those 1/2 hr dispatches.
This is how i go about my flight planning, I might be full of crap but it seems to work for me, and they still give me a PPC every year (for a fee of course)
Hope this helps and happy flying!!!
Its kinda hard to pull out the manual everytime for those 1/2 hr dispatches.
This is how i go about my flight planning, I might be full of crap but it seems to work for me, and they still give me a PPC every year (for a fee of course)
Hope this helps and happy flying!!!
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justplanecrazy
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- Joined: Wed Feb 25, 2004 1:57 pm
I think he was saying that at a certain altitude with cruise settings, your TAS and IAS will both be higher in the cold air, not that the difference between your TAS and indicated airspeed will be higher.
We have no effective screening methods to make sure pilots are sane.
— Dr. Herbert Haynes, Federal Aviation Authority.
— Dr. Herbert Haynes, Federal Aviation Authority.
Thinner air gives a higher TAS, be it warmer air or less dense air found higher up. Cold air gives shorter take-off and landing numbers, slower cruising TAS, and higher IAS. The Seminole indicates 25kts more in the middle of winter vs. middle of summer...but TAS is the pretty much the same.
pika, we are talking performance, not conversion. You will not get the same CAS at different temperatures.
For the rest of you, it depends on a lot of things. Is the aircraft turbocharged? Are you running at optimum altitude? Is the throttle wide open to get 75% power or do you have some power left?
For the rest of you, it depends on a lot of things. Is the aircraft turbocharged? Are you running at optimum altitude? Is the throttle wide open to get 75% power or do you have some power left?
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justplanecrazy
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- Joined: Wed Feb 25, 2004 1:57 pm
Pika... if you climb in a C172 powered aircraft in the middle of the summer and put in 75% cruise power, you will not neccessarily have a higher true airspeed.
Your CAS will definately be lower and possibly low enough to make your TAS lower than in the winter as well. This is because the warm air may decrease engine performance more than it increases TAS vs. CAS.
Yes if you increased the power until you had the same CAS as in the cold air, the TAS will be lower in the cold air.
So to contradict your statement, warmer air does not always give a higher TAS regardless.
Your CAS will definately be lower and possibly low enough to make your TAS lower than in the winter as well. This is because the warm air may decrease engine performance more than it increases TAS vs. CAS.
Yes if you increased the power until you had the same CAS as in the cold air, the TAS will be lower in the cold air.
So to contradict your statement, warmer air does not always give a higher TAS regardless.
We have no effective screening methods to make sure pilots are sane.
— Dr. Herbert Haynes, Federal Aviation Authority.
— Dr. Herbert Haynes, Federal Aviation Authority.
I don't think anyone answered eemami's question...at least in any simple terms...so here goes...
An aircraft's airspeed indicator is only accurate at sea level on a standard day and it displays Indicated Airspeed (IAS). Temperature and altitude will cause the airspeed indicator to read incorrectly due to the difference in air density and will need to be corrected somehow.
However, before before we do that, the airspeed indicator is subject to other errors that are specific to the aircraft (like position error) that need to be fixed. The corrected values are usually found in the form of a chart in the POH and this corrects the IAS to Calibrated Airspeed (CAS).
Because the aircraft rarely flies at sea level on a standard day, the CAS must now be corrected for the planned cruising altitude and associated temperature. This calculation is done using an E6B or similar. For example, 100 Kts CAS (KCAS) at 10,000 feet and -15C gives you a TAS of 114 KTAS.
In perfectly still air, your groundspeed should be 114 Kts. Wind, of course, will have an effect depending on its strength and direction. A resultant 20 Kt tailwind will give a groundspeed of 134 Kts.
Estimated time enroute (ETE) then, is distance to destination divided by groundspeed multiplied by 60 to give you the number of minutes to destination.
100 nm / 134Kts x 60 = 45 minutes
Thats just a basic explanation so I hope that makes sense eemami.
An aircraft's airspeed indicator is only accurate at sea level on a standard day and it displays Indicated Airspeed (IAS). Temperature and altitude will cause the airspeed indicator to read incorrectly due to the difference in air density and will need to be corrected somehow.
However, before before we do that, the airspeed indicator is subject to other errors that are specific to the aircraft (like position error) that need to be fixed. The corrected values are usually found in the form of a chart in the POH and this corrects the IAS to Calibrated Airspeed (CAS).
Because the aircraft rarely flies at sea level on a standard day, the CAS must now be corrected for the planned cruising altitude and associated temperature. This calculation is done using an E6B or similar. For example, 100 Kts CAS (KCAS) at 10,000 feet and -15C gives you a TAS of 114 KTAS.
In perfectly still air, your groundspeed should be 114 Kts. Wind, of course, will have an effect depending on its strength and direction. A resultant 20 Kt tailwind will give a groundspeed of 134 Kts.
Estimated time enroute (ETE) then, is distance to destination divided by groundspeed multiplied by 60 to give you the number of minutes to destination.
100 nm / 134Kts x 60 = 45 minutes
Thats just a basic explanation so I hope that makes sense eemami.
