Mach-Number to Airspeed Conversion Above 65,000 Feet
Joined: Dec 2010
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From: Europe
I posted this once, then pulled it because Jane Doh is almost certainly an anti-sciolist, but for those who are genuinely interested, the speed of sound expressed in EAS is independent of temperature. You only need to know pressure altitude and then multiply by Mach Number to get the flight EAS.
Values:
Press.Alt Speed of sound
65000 ft - 156.02 kts EAS
70000 ft - 138.35 kts EAS
75000 ft - 122.69 kts EAS
80000 ft - 108.8 kts EAS
Values:
Press.Alt Speed of sound
65000 ft - 156.02 kts EAS
70000 ft - 138.35 kts EAS
75000 ft - 122.69 kts EAS
80000 ft - 108.8 kts EAS
Thread Starter
Joined: Dec 2010
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From: New York & California
PBL
Okay gamma is the ratio of specific heat at constant pressure vs ratio of specific heat at constant volume. What are the formulae for specific heat at constant pressure and specific heat at constant volume?
Turbine D
I've already went online to find it...
PBL
Which questions? I explained what the reason I was asking about the units of pressure because I was trying to convert the TAS figures for mach (sea-level) into IAS readings at altitude.
CliveL
Sciolist means an amateur, right?
Pressure altitude means the pressure at a given altitude?
sqrt(gamma x R x T)
Turbine D
To find the Greek Alphabet, Γοογλε ιτ !
PBL
no, I want you to answer my questions.
CliveL
Jane Doh is almost certainly an anti-sciolist
You only need to know pressure altitude and then multiply by Mach Number to get the flight EAS.
Joined: Jan 2011
Posts: 660
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From: England
You only need to know pressure altitude and then multiply by Mach Number to get the flight EAS.
Values:
Press.Alt Speed of sound
65000 ft - 156.02 kts EAS
70000 ft - 138.35 kts EAS
75000 ft - 122.69 kts EAS
80000 ft - 108.8 kts EAS
Values:
Press.Alt Speed of sound
65000 ft - 156.02 kts EAS
70000 ft - 138.35 kts EAS
75000 ft - 122.69 kts EAS
80000 ft - 108.8 kts EAS
If I am reading you correctly you are saying that the EAS in the right hand column is the local speed of sound (Mach 1) at the pressure altitude in the left hand column.
How do we get from the pressure altitudes that you have quoted, to the EAS values by multiplying by Mach 1?
Joined: Dec 2010
Posts: 291
Likes: 2
From: Europe
If I am reading you correctly you are saying that the EAS in the right hand column is the local speed of sound (Mach 1) at the pressure altitude in the left hand column.
How do we get from the pressure altitudes that you have quoted, to the EAS values by multiplying by Mach 1?
How do we get from the pressure altitudes that you have quoted, to the EAS values by multiplying by Mach 1?
I didn't say multiply by Mach 1, I said multiply by Mach Number; i.e. the EAS at say Mach 1.4 at 65000 ft would be 218.4 kts
Perhaps I should have written "you only need to know the pressure altitude to get the speed of sound in kts EAS and then multiply that by Mach Number to get the flight EAS"
CliveL
Joined: Jan 2011
Posts: 660
Likes: 20
From: England
Sorry Clive,
When I read you post I thought that you were saying "Multiply the pressure altitude by the mach number and you get the EAS at that mach number".
For one fleeting moment I thought that this was going to be one of those really magical moments like the day I was first introduced to Calulus all those decades ago.
Now I see that what you were really saying was "If you have a table of pressure altitudes against the EAS for local speed of sound, then just multiply this EAS by any given mach number and you will get the EAS for that mach number at that pressure altitude".
When I read you post I thought that you were saying "Multiply the pressure altitude by the mach number and you get the EAS at that mach number".
For one fleeting moment I thought that this was going to be one of those really magical moments like the day I was first introduced to Calulus all those decades ago.
Now I see that what you were really saying was "If you have a table of pressure altitudes against the EAS for local speed of sound, then just multiply this EAS by any given mach number and you will get the EAS for that mach number at that pressure altitude".
Joined: Dec 2010
Posts: 291
Likes: 2
From: Europe
Now I see that what you were really saying was "If you have a table of pressure altitudes against the EAS for local speed of sound, then just multiply this EAS by any given mach number and you will get the EAS for that mach number at that pressure altitude".
Clive
Thread Starter
Joined: Dec 2010
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From: New York & California
John Farley
I'm sorry that I didn't properly read your messages. I should have paid more attention.
BTW: In regards to the video that Pugilistic Animus showed, you're a very good narrator
Pugilistic Animus & John Farley
Fascinating video. I never knew the Harrier used reaction control systems
I'm sorry that I didn't properly read your messages. I should have paid more attention.
BTW: In regards to the video that Pugilistic Animus showed, you're a very good narrator
Pugilistic Animus & John Farley
Fascinating video. I never knew the Harrier used reaction control systems
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From: Germany
We're doomed
PBL, who on earth do you think would have any interest in building such an incredibly sophisticated system as Jane-Doh ... and come up with the idea to of all things test it on an aviation forum? I can see only one logical conclusion: Jane-Doh is Skynet!
Thread Starter
Joined: Dec 2010
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From: New York & California
TEOTWAKI
Yeah, that's it 
PBL, who on earth do you think would have any interest in building such an incredibly sophisticated system as Jane-Doh ... and come up with the idea to of all things test it on an aviation forum? I can see only one logical conclusion: Jane-Doh is Skynet!
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From: Manchester
What are the formulae for specific heat at constant pressure and specific heat at constant volume?
I'm not entirely sure what you mean by specific heat, are you attempting to apply pV=nRT to this or something else?
