Some of the Muscat Controllers get impatient and outright testy with westbound pilots who are unable to immediately establish contact at the eastern boundaries: RASKI, PARAR, and especially at ASPUX, the furthest waypoint which is virtually beyond the limit of VHF reception, even at FL400.
One of the problems is frequency congestion with Mumbai HF as crews are trying to check out with Mumbai Radio. Another problem is that some of the onboard VHF receivers and transmitters are weaker than others and pilots may not immediately make contact with Muscat Center on 128.15, or on 123.95 until several minutes inside Muscat airspace. This is especially true of airplanes that are entering at a lower Flight Level, as VHF reception and transmission is equivalent to line-of-sight.
Adding to the Muscat Controllers' workload are the frequent requests by westbound pilots to advise Mumbai on the landline that "checkout" via HF was not possible.
Muscat Controllers should be aware of these limitations, and they should understand that pilots do not intentionally establish belated contact.
