Both Collopy and Chatter state that the plane had 1100 U.S. gallons on board but there is a conflict in their statements.
Yes, but easily explainable without jumping to the conclusion that they were wrong.
Collopy said that a 100 gallon tank was half full while Chatter said an 81 gallon tank was half full. There are no 100 gallon or 81 gallon tanks in the fuselage but there are 102 gallon and 81 gallon tanks in each of the wings.
True.
Earhart lost control of the plane on takeoff from Hawaii so she would be loath to have a lateral fuel imbalance on takeoff at Lae so is likely that she wouldn't just leave one tank in just one of the wings half full but would leave a tank on the other side half full also.
How can you possibly know what Earhart would be loath to do? I imagine that you would be loath to set off to fly around the world in 1937 without knowing Morse code. I sure would. The 81 and 102 gallon wing tanks were in the center section inboard of the engines and gear. A 300 lb. discrepancy side-to-side that close to the fuselage and inboard of the gear in a 15,000 airplane is hardly worth worrying about.
Supporting this theory is the discrepancy in the size of the tanks described by Chatter and Collopy. If one of them looked in the tank and passed the information on the other guy then they would have the exact same size for the tank so it didn't happen this way.
There was no way to "look in the tanks." The tanks were buried in the wings. As shown in the
Fuel System research bulletin, the 16 and 81 gallon tanks share a filler port. For fueling and fuel gauge purposes the two tanks are treated like a single 97 gallon tank.
If they each looked in the same tank that was half full then, again, they would have stated the same size. Based on this it is reasonable that they were each looking in different tanks, one in the right wing and one in the left wing. They both said they saw a tank half full ...
No they didn't. Neither one of them said anything about seeing a tank half full.
Chater said,
"This tank was approximately half full and it can be safely estimated that on leaving Lae the tank at least 40 gallons of 100 octane fuel ..." He didn't say how he knew the tank was approximately half full.
Collopy said,
"One tank contained only 50 gallons of its total capacity of 100 gallons." Ditto.
If the wing tanks were not full, the only way to know how much fuel was in them was from the fuel gauges. From photos of the Electra cockpit it appears that the the fuel gauge for each of the "97 gallon" tanks was a Kollsman 180. The gauge read from 0 to 100 gallons in five gallon increments (even though the combined tanks held only 97 gallons). Chater looks at the gauge and sees that it reads roughly 50 gallons. He knows that the gauge is actually for two tanks, a 16 and an 81, because he has a Lockheed Electra of his own. If the gauge is reading 50 gallons then the 16 gallon tank is empty and the 81 gallon tank is down about 34 gallons - about 47 gallons remaining. So he says,
"This tank was approximately half full and it can be safely estimated that on leaving Lae the tank at least 40 gallons of 100 octane fuel ..." Safe guess.
Collopy looks at same gauge and sees the same thing but Collopy doesn't know the particulars of the Lockheed 10. All he knows is that the gauge goes from 0 to 100 gallons and that the needle reads about 50, so he says,
"One tank contained only 50 gallons of its total capacity of 100 gallons."Based on this I believe that it is quite likely that they only had about 1050 U.S. gallons on board when they took off from Lae.
I think it's more likely that the actual load was more like 1,107 U.S. gallons but 1,100 is a safe conservative figure.
Ric