CP/PNR question Ground Class CPL

[Shrineel]

In the event of return to departure point 10000 lbs of fuel is available, when back over the departure point. The flight reserves being carried are \ 15000lbs. the average fuel flow is 5000 lbs/hr. TAS 400 K & there is a dead headwind of 100K. theposition of PNR is relation to the CP will be a. 200 nm. Furtherb. 250 nm furtherc. 188 nm lessd. 188 nm further

It would be better if someone post the answer along with explanations

[VariablePitchP]

Originally Posted by Shrineel

In the event of return to departure point 10000 lbs of fuel is available, when back over the departure point. The flight reserves being carried are \ 15000lbs. the average fuel flow is 5000 lbs/hr. TAS 400 K & there is a dead headwind of 100K. theposition of PNR is relation to the CP will be a. 200 nm. Furtherb. 250 nm furtherc. 188 nm lessd. 188 nm further

It would be better if someone post the answer along with explanations

Firstly, formatted question

In the event of return to departure point 10000 lbs of fuel is available, when back over the departure point. The flight reserves being carried are \ 15000lbs. the average fuel flow is 5000 lbs/hr. TAS 400 K & there is a dead headwind of 100K. theposition of PNR is relation to the CP will be

a. 200 nm. Further

b. 250 nm further

c. 188 nm less

d. 188 nm further


PNR vs CP — worked example

• TAS: 400 kt
• Headwind: 100 kt
• Fuel flow: 5,000 lb/hr

• Groundspeeds
• Outbound GS = 400 − 100 = 300 kt
• Return GS = 400 + 100 = 500 kt

Fuel per NM

• Outbound: 5,000 / 300 = 16.67 lb/nm
• Return: 5,000 / 500 = 10 lb/nm
• Total per extra nm out-and-back = 26.67 lb/nm

Fuel available

• Reserves carried: 15,000 lb
• Fuel required over DP on return: 10,000 lb
• Extra usable fuel = 5,000 lb

• Distance beyond CP
• 5,000 / 26.67 ≈ 188 nm

Conclusion

PNR is 188 nm further than CPAnswer: d.

Courtesy of CaptainGPT, so treat with scepticism