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Today, Prime Minister Narendra Modi flew into Cochin from Delhi on Indian Air Force One, operated by an Indian Air Force Boeing 737-700 Boeing Business Jet (BBJ) with tail number K5014. The way in which the airplane was flown was interesting, and different from the way in which a similar aircraft operating for a scheduled airline is flown. We compare the way in which the military 737 was flown, with the way in which a commercial 737-800 was flown on the same route.
The 737-700BBJ’s lateral flight path is compared with the lateral flight path of a Boeing 737-800 VT-SZA operated by SpiceJet today on Delhi-Cochin as SG 561. What stands out is that the flight path of the military 737 is curvy, and not straight unlike the SpiceJet 737, strongly indicating that the flight was manually controlled, either by being hand flown throughout or by manual heading inputs to the autopilot. It does point to neither the autopilot’s VOR/LOC function, nor the FMS-controlled lateral navigation being used.
The vertical flight path shows that the Prime Minister’s flight (image on the left shows Him beside the 737 at Cochin) was not optimized for fuel burn. The aircraft climbed to 31,000ft (odd level altitude) when headed in the easterly direction, and as it changed direction over Hyderabad to a westerly direction, the aircraft descended to 30,000ft (even altitude). A BBJ, usually being light, can fly much higher than 31,000ft. The optimum altitude for an airplane gets higher as it gets lighter, and it could have step climbed rather than step-descended over Hyderabad.
The SpiceJet 737, in contrast, flew at 37,000ft till over Hyderabad. By then, the airplane was lighter, having burnt most of the flight’s trip fuel. Over Hyderabad, when turning towards Cochin, it step climbed to 38,000ft – just as one would expect for optimal fuel burn.
A valid argument would be the winds at altitudes that could have impacted the military 737’s decision to fly at a lower altitude. The SpiceJet flight and the military 737 flight were 5 hours apart. However, IndiGo’s VT-IEM operating 6E 289 DEL-COK took off just 28 minutes after the Air Force 737, climbed to 35,000ft and then to 36,000ft over Hyderabad. IndiGo’s aircraft in fact picked up 13 minutes enroute, to land just about 15 minutes after the Air Force 737, clearly showing that winds at higher altitude were not unfavourable.
The intent of this piece isn’t to highlight who flies better, but rather to appreciate some of the differences between air transport flights in the military and in the commercial world. Vastly different priorities may explain the differences in flying. In the airline world though, it is all about minimising costs at every little opportunity.
Thanks to Karthik Kumar for the image of K5014.
Atul Bhatia said:
Truth be told, the differences in the route are insignificant. The first kink in the flight plan that appears in the BBJ’s flight is the actual route that all aircraft are expected to fly – W20S. In the interest of fuel savings, we normally ask for (and get) direct from waypoint AKELA to IBANI; perhaps AF1 did not get the direct, perhaps it did not ask for it. Or perhaps at FL300 Agra was unable to grant a direct through its airspace in the interest of safe separation from other military traffic.
As to why it chose to fly at FL300, beats me. Perhaps it was to meet the target door opening time, and reaching early would be counterproductive. Sadly, military aircraft do not have an incentive to save fuel the way commercial aircraft do.