Dgca Atpl Critical Point Question - Please Help!

[AZFlyUSA]

Fellow aviators, I am self studying for DGCA ATPL composite paper (Feb Session), I would like to get tutoring from Surinder but did not have time on this attempt, I am planning on attending Surinder's class on April 1st so hopefully I can be fully prepared for the April session.

Whilst self studying, I have come across a problem that I can't seem to solve, so please can anyone shed some light!

ON A FLIGHT FROM P TO R VIA Q THE AIRCRAFT IS REQUIRED TO RETURN TO Y VIA Q IN CASE OF ENGINE FAILURE. TAS ON 4 ENGINES IS 500KT & IN CASE OF 3 ENGINES IT IS 420KT, THE ROUTE DETAILS ARE BELOW;

STAGE WIND COMP DISTANCE
P-Q -25 965
Q-R -45 900
Q-Y +30 240

A) FIND THE DISTANCE TO THE CP BETWEEN R & Y.

B) IF FOB IS 38000KG, RESERVE 6500KG, F/C 6300KG/HR 4 ENG, F/C5600KG/HR 3 ENG, FIND TIME & DISTANCE TO PNR, THE A/C RETURNING TO Y.

( I managed to figure out the PNR, it should be DPNR 1572nm & TPNR 3 Hrs, 22mins.

Thanking you guys & gals in advance.

[PappyJ]

Try this.....

Distance to critical point (nm) = D x gsA / gsB + gsA
Where:
D = total distance from point A to point B (nm)
gsA = ground speed from critical point to go back to point A, and
gsB = ground speed from critical point to proceed to point B

[jetzup]

answer:
distance to cp is 1353 nm and time to cp is 2 hours 53 minutes,
distance to pnr is 1572 nm and time to pnr is 3 hours 22 minutes.

Had a similar problem and this is what I learned from my instructor

[AZFlyUSA]

Thank you guys very much for taking the time to post. Jetzup, I also get the same answers which I know are correct, please can you explain though how you got the answer to CP distance & time, if you could show the working out for me, I would really appreciate it.