1

I try to calculate the correction of cold temperature for altimeter , i use for this the equation 24 of the Engineering Sciences Data Unit (ESDU) publication but it give me very high number . if i take for example the given conditions altitude of aircraft 1000 ft 0 ft for aerodrome altitude t0 288 K temperature deviation from the ISA = 259.9812 L0 = 0.001981 the result is 599777.4389 ft is too big , the expected result is 60 ft So where is mistakes ? enter image description here

EDIT : So i corrected the ISA dev according to what Ralph said but the result still incorrect i joint the step of calculation : enter image description here the expected result is 60 ft enter image description here

Namster
  • 11
  • 3
  • 2
    259 degree temp dev from ISA is unreasonable by an order of magnitude. You may be mixing C and K units there. Please fix that & edit your question accordingly. – Ralph J Jan 24 '21 at 03:09
  • Infact 288degK at 0 ft altitude is = 15degC = ISA, so intended dev from ISA seems to be zero for purpose of the example question. – skipper44 Jan 24 '21 at 04:34
  • I agree, you are mixing temperature scales (K and C) and hence your incorrect result. – Juan Jimenez Jan 25 '21 at 01:55
  • T aerodrome = 273K, T isa = 288K. so dT = 15K. Applying the correct formula (see Namsters' answer below) gives 15/0.001981 * ln (1+ 1.981/288) = 51.90ft (since dH aerodrome = 0).

    The table from PANS OPS Doc 8168 uses an approximation which works for temps above -15C (4 times the alt above the aerodrome in thousands of feet, times dT which equals 60).

     – Sacha Jul 21 '22 at 15:22

1 Answers1

1

Finaly i have found the answer the error is on all book that published the equation there is the true equation enter image description here

Namster
  • 11
  • 2