Range difference between manufacturer marketing and the real world

[tuna]

Skip towards the end if you dont need the backstory:

Some of you might be aware, there is a minor political controversy over US Speaker of the House Nancy Pelosi and her use of US military jets for personal transportation to and from her home district in san francisco and Washington, DC.

The controversy goes that she has been unsatisfied with the military Gulfstream III that was provided to her predecessor and that her aides have spent a lot of time requesting that larger jets be made available. This includes military Gulfstream V and to the glee of right-wing rumorspreaders, even a military Boeing 757 (according to her office, it was only once when no other plane was available).

I don't care much about the whole situation. She's the Speaker of the House, 3rd in the line of presidential succession, and she should definitely not be flying commercial. That was the decision that was made after 9/11 with a republican president and congress.

My interest is that her office, in an attempt to deflect criticism, has said that the issue was never about 'bigger' jets and that they have only ever requested jets that could make the flight from DC to SFO nonstop. They claim that when flying back west, with wind conditions that are common during the winter, they often have to stop to refuel.

I know nothing about aviation, but this smells like bullshit to me. The current iteration of the G3 is marketed as having a 3,800 nmi range. The plane that she was using, the US military's C-20B, which is basically the older version of the G3, is listed as having a 3,700 nmi range. I know that these marketed ranges are based on a lot of assumptions like having only 1,600 lbs of passengers and cargo, and minimum reserves, and ideal weather conditions. It also seems to me (but I know nothing about aviation) that attempting to fly the great circle route between those points would put you right against the jet stream. But the great circle distance from Washington Dulles to San Francisco Intl is only 2,100 nmi! Is it really possible that a G3 couldn't make it coast to coast nonstop?

I feel it more likely that there was one occasion where she had to be rerouted around a storm and needed to stop to refuel , and that serves as the backstory to a lame lie.

I don't know much about aviation but I know that the G3 is marketed as having "continental", nonstop coast to coast range. Even the G2 which is marketed as having 3,400 nmi range is marketed as having that same capability. Same thing for the Bombardier Challenger 300 which is only advertised as having 3,100 nmi range.

So it it really possible that a "3,700 nmi" plane can't fly 2,100nmi west in the winter?

 

[BoeingBoy]

Is it really possible that a G3 couldn't make it coast to coast nonstop?

Anything is possible. The first thing that comes to mind is the departure airport - did she insist on leaving from DCA or use IAD? I could see the runways at DCA limiting the T/O weight enough to make the difference.

As you mentioned, then there's load. While it's hard to believe that enougn passenger/baggage weight would be carried to limit the range that much, adding a range restriction due to passenger/baggage weight to a headwind restricted range could make a stop necessary.

Jim

 

[tuna]

Anything is possible. The first thing that comes to mind is the departure airport - did she insist on leaving from DCA or use IAD? I could see the runways at DCA limiting the T/O weight enough to make the difference.

Lets not count that. There are plenty of full length runways in the area.

As you mentioned, then there's load. While it's hard to believe that enougn passenger/baggage weight would be carried to limit the range that much, adding a range restriction due to passenger/baggage weight to a headwind restricted range could make a stop necessary.

Jim

Thats crazy to me. Is there some reason that this is different then flying somewhere farther, say Tokyo? How much range would you need then?

 

[BoeingBoy]

Lets not count that. There are plenty of full length runways in the area.

Without knowing more than was in the 1st post, I'm not sure we can discount anything. Certainly there are longer runways in the area - both Dulles and Andrews come to mind. But if Pelosi insisted on departing from Reagan those longer runways are no more useful the I95.

Thats crazy to me. Is there some reason that this is different then flying somewhere farther, say Tokyo? How much range would you need then?

Although I know nothing about the GIII other than what you posted, range in most airplanes is a function of load vs fuel. Above some gross weight point, more load means less fuel so less range is possible. As I said, I can't see this being a factor by itself - how many people/bags could Pelosi need for a trip to California? But adding in a particularly strong headwind and it might be enough to require a fuel stop. If Grumman publishes still air range, a 150 knot headwind would effectively reduce range by about 650 nm on a transcon flight.

Of course, there's the alternate factor - how far away is a suitable alternate on a given day. Every mile needed to reach a suitable alternate is a mile less that can be flown to the destination.

Given the range figures in the 1st post it's unlikely a GIII would need a fuel stop - unless it departed from DCA. But unlikely isn't the same as impossible, and there could be a combination of factors that could cause a fuel stop after departing from Dulles or Andrews.

Jim