Indigo Call letters for Freshers
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@wings of fire
Q1) An a/c is descending at a contant mach number. If the a/c is descending through an inversion layer, the RAS will:
a)remain constant
b)increase
c)decrease
d)decrease then decrease more slowly
Answer is b) increase.
however during descent in inversion, temp decreases at lower altitude. so, LSS decreases. since M.no = (TAS / LSS), therefore TAS should also decrease, in order for M.No to remain constant.
Yes, density increases at lower altitudes.
Now, RAS=(1/2)*density*(TAS squared).
Therefore effect of decreasing TAS is more, then increase of density.
so answer should be c) decrease.
Can anyone explain?
a)remain constant
b)increase
c)decrease
d)decrease then decrease more slowly
Answer is b) increase.
however during descent in inversion, temp decreases at lower altitude. so, LSS decreases. since M.no = (TAS / LSS), therefore TAS should also decrease, in order for M.No to remain constant.
Yes, density increases at lower altitudes.
Now, RAS=(1/2)*density*(TAS squared).
Therefore effect of decreasing TAS is more, then increase of density.
so answer should be c) decrease.
Can anyone explain?
TAS=RAS + Density error.
In general, you can assume that the inversion doesnt make a difference to the CAS.
so, CAS increases in a descent and decreases in a climb with Mach constant.
cheers,
P
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@ aviator 09
Perfecto .Full marks to u. My error was for 45 N latitude - I was calculating hourly real drift with 45 mins of ERW simultaneously. Thanks any idea for remaining 1 question
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@ puneeth
Buddy 1/2*rho * (v square) is formula of dynamic pressure- but that is also called indicated airspeed.
And since , RAS = IAS corrected for position error.
and position error is negligible. therefore we can safely say, RAS=IAS
Hence, RAS = 1/2* rho * (TAS squared)
and this is how we were taught , when i took classes from surinder sir.
Other students of sir, correct me if I am wrong
By the way, what's your email id
And since , RAS = IAS corrected for position error.
and position error is negligible. therefore we can safely say, RAS=IAS
Hence, RAS = 1/2* rho * (TAS squared)
and this is how we were taught , when i took classes from surinder sir.
Other students of sir, correct me if I am wrong
By the way, what's your email id
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@wings of fire
Hi mate,
not sure about the classes, i havent had the chance to attend them. Just going by what i understood from Oxford books.
either way, the general idea is that as density increases CAS increases.
i was doing some reading on the same topic and found this, hope it helps.
Relation beween CAS, TAS, MN, Temp and pressure - ATP Forum
cheers,
P
not sure about the classes, i havent had the chance to attend them. Just going by what i understood from Oxford books.
either way, the general idea is that as density increases CAS increases.
i was doing some reading on the same topic and found this, hope it helps.
Relation beween CAS, TAS, MN, Temp and pressure - ATP Forum
cheers,
P
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@wings of fire and @puneeth
EAS(without compressibility error EAS=CAS) and Mach number are related by:
EAS = M * LSS * sqrt(Ps / Pstd)
Where
Ps = static pressure
Pstd = standard pressure (1013.25 hPa)
This is the same equation I had for true airspeed, except with pressure ratio instead of temperature ratio. Consolidating the constants it becomes:
EAS = M * 20.78 * sqrt(Ps)
The point to note is that Equivalent airspeed is a function of mach number and pressure, temperature is irrelevant.
Reference: Relation beween CAS, TAS, MN, Temp and pressure - ATP Forum
EAS(without compressibility error EAS=CAS) and Mach number are related by:
EAS = M * LSS * sqrt(Ps / Pstd)
Where
Ps = static pressure
Pstd = standard pressure (1013.25 hPa)
This is the same equation I had for true airspeed, except with pressure ratio instead of temperature ratio. Consolidating the constants it becomes:
EAS = M * 20.78 * sqrt(Ps)
The point to note is that Equivalent airspeed is a function of mach number and pressure, temperature is irrelevant.
Reference: Relation beween CAS, TAS, MN, Temp and pressure - ATP Forum
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TAS=RAS + Density error.
Puneeth, You skipped one of the major errors.!
@ wings of fire
I'd get back to you as and when I solve those object revision questions and I derive the explanation behind that question.
Yes, you're correct when you say that CAS and RAS can be taken to be the same and hence the same formula too, 1/2 rho V squared. I took the same classes as you did. It has always worked for me, but cant still figure out the reason here.
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EGPWS
Could anyone clarify about Mode 6 and 7 in EGPWS.
Mode 7 is for windshear alert below 1500 feet and gives windshear warning both during approach and takeoff.
similarly, Mode 6 gives bankangle warning. Is the bank angle warning only during approach or also during t/o?
Mode 7 is for windshear alert below 1500 feet and gives windshear warning both during approach and takeoff.
similarly, Mode 6 gives bankangle warning. Is the bank angle warning only during approach or also during t/o?