View Full Version : Boeing 777 EGPWS Pull UP following GPS Jamming

31st Aug 2023, 16:21
Routing from Europe to India via the middle east it is common to encounter GPS jamming/spoofing over the middle east. As a result one or both of the GPS systems goes off line. Sadly, and for reasons beyond my technical comprehension sometimes one or both of the systems will remain off line for the balance of the flight. The first difficulty this presents is remaining within required RNP over the Indian Ocean, not really a huge issue as its never too far out and once a DME comes back in to range accuracy is good enough.

The major issue is that on approach into BOM an EGPWS warning is generated. The operators current policy is that such a warning CAN NOT be ignored (even if the information in the FMC indicates that the GPS is unreliable and a spurious warning may be about to occur). Anecdotal evidence suggests there have been about 5 so far.

I believe other operators have produced an internal procedure that involves recycling the MMR circuit breakers once the GPS jamming has ceased, this would appear to cure the problem. Unfortunately as apparently Boeing will not sign off on this my operator will not sanction it.

So, what to do:

Apply full power and pitch 20 degrees nose up, ignore the warning ( Captains perogative perhaps) despite clear guidance in the ops manual that I must not, reset the MMR CBs anyway, depite guidance that I must not, demand a re-route around the middle east at the planning stage as I wish to avoid a GPWS warning.

Management at the operator do not seem to be addressing this with the degree of urgency it requires, I know the first warning occurred at LEAST 3 months ago. Fortunately I'm not planned to head that way for a while but I would appreciate any advice others have to deal with this problem, particularly procedures introduced by any other airlines.

1st Sep 2023, 10:38
I'm Airbus no Boeing but there is an FCOM procedure to switch off EGPWS if the airfield you are going to is non WGS 84 compliant and possibly some other cases such as failure IIRC.