Three weeks into the disappearance of Malaysia Flight 370, the reporting has actually gotten worse.
CNN is trying to rent 777s as set-pieces. They can't, so they rent a full-motion Level D simulator at what is normally about $5,000/hr. I hope they negotiated a discount.
The author of Everyone's Favorite Theory (TM) has revealed himself to be rather confused about the manner in which jet pilots navigate the globe. (Do a text find of the word "rotation." Hilarity ensues. Hint: the Earth doesn't spin underneath you while you're in the air.)
And virtually every media organization on earth is now reporting that MH 370 is no longer governed by the laws of physics, flying "faster" than previously thought during its 7.5 hours aloft and yet somehow - through magic, I assume - covering less distance.
Below the fold, I will try and address that third bit, which is driving everyone in aviation absolutely crazy.
SIMPLE MATH: If two identical airplanes fly identical routes in identical winds and temperatures and both are aloft for 7.5 hours, the one that flies faster will travel a greater distance.
Period.
Thus, when one is reporting, as every major outlet is right now, that MH 370 exhausted its fuel by flying faster and therefore covered less ground than previously thought, what one is really saying is there was no 8:11am "ping," because a higher fuel burn would have reduced the craft's endurance and it would have run out of fuel prior to the 7.5 hours for which its fuel load should have allowed.
Aircraft don't work in terms of miles per gallon because wind is too great a variable. Fuel consumption in aviation is therefore always calculated in terms of time, which is ENDURANCE. Higher power settings can indeed lower endurance. But RANGE is a function of groundspeed. In fact, Range = Endurance (in hours) x Groundspeed.
But nobody's reporting it that way and no one seems to be asking the operative question:
Was there an 8:11 ping or not? If there wasn't, I'd say the people at Inmarsat and their befuddled dependents in the Malaysian government have a lot to answer for, since they told 239 separate families that everyone died near the 40th Southern Parallel in the Indian Ocean based on a supposed 8:11 am final ping.
If there was an 8:11 am ping, please don't insult our intelligence by saying the plane went down short of the old search area because it flew faster and burned more fuel. It flew at least 7.5 hours, as established by the 8:11 ping. It could have covered less distance by flying slower in that 7.5 hours. But flying faster over that 7.5 hours would definitely cause it to travel farther.
7.5 hours just so happens to be the exact amount of time the plane was fueled and loaded to fly - under normal takeoff, climb and cruise circumstances - when it left Kuala Lumpur.
It had a Zero Fuel Weight (aircraft + pax & cargo) of 384,486 lbs. It carried 108,247 lbs of fuel for a total Taxi Weight of 492,733 lbs. (The link shows tonnes. I converted.)
RR Trent 892 engines on the 777 burn on average about 13,400 lbs of fuel per hour in cruise at altitude. It will burn about 21,000 lbs in the 1st hour due to the taxi, takeoff and climb. In the case of MH 370, this leaves 86,247 lbs of fuel for the remainder of the trip.
87,247 / 13,400 = 6.5 hours. Total endurance, 7.5 hours.
Corresponds rather nicely with the 8:11am ping. It also happens to be a perfectly logical fuel load for a 6 hour international flight (ICAO fuel regs are here).
It also seems to suggest that the aircraft flew a rather normal profile. There are really not that many ways to fly an airplane and still achieve the book endurance. It's a small window. It involves carefully managed speeds and altitudes. Step climbs as the plane burns fuel and gets lighter. The FMC will set almost every variable for you, from EPR to altitude.
The probability of an aircraft achieving the exact endurance for which it was fueled would be near zero if it fluctuated wildly in altitude, or flew for any period of time at any altitude/speed combination outside the very narrow range of OPTIMAL combinations from which the published endurance figures are derived.
Is there another altitude/speed combination that might allow for the book endurance and yet cover less range? Possibly. But it doesn't involve a faster airplane. Quite the opposite.
It may be possible that an airplane flown at an indicated airspeed very near its best glide speed ("Vg" - somewhere between 240-260 KIAS, decreasing slowly throughout the trip as the plane got lighter) and at a relatively low altitude. Yes, contrary to popular belief, jet engines actually burn less fuel per pound of thrust per hour at sea level than they do in high altitude cruise. It's the higher true airspeeds and the favorable effects of compressibility on drag that give jets greater range at high altitude and Mach numbers.
I don't have access to enough performance data to know what altitude/airspeed combo outside the normal cruise regime would achieve 7.5 hours endurance on MH 370's exact fuel load, or if there even is such a combination. What I can absolutely guarantee is that flying low and slow wouldn't shorten the fuel exhaustion point by a mere 500 nautical miles (as the "new search area" would indicate). It would shorten it by more than 1300 nm because you're talking about the difference between a true airspeed of 480 knots and somewhere in the range of 310 kts.
So until someone discredits the 8:11am ping, the MSM has a lot of explaining to do on the matter of the "faster airplane covering less ground in 7.5 hours."