Preventing Fuel Leaks

Published Nov. 19, 2013
By Mr. Len Cwiklik
C-17 System Safety Manager

Winter 2013/2014 -- In the past few months, I've seen safety reports from the C-17 community (USAF and international customers) about fuel leaking from cargo and the accuracy of Center of Gravity (CG) markings on vehicles and heavy equipment. As we increase the tempo of removing equipment from the Area of Responsibility (AOR), I want to increase the awareness of the problem for aircrews, aerial port personnel, and people preparing cargo for air shipment.

As we begin to move the equipment and cargo out of many bases, the documentation certifying that the cargo has been properly prepared for air shipment may not receive the highest priority. One of the most frequent pieces of equipment involved with fuel leaks or fumes in the cargo compartment is generators. These items have significant fuel capacity and can be shipped with as much as three-fourths of a tank of fuel. In addition, these units have vapor recovery lines that should be purged as part of the preparation because they can vent fuel fumes as the pressure in aircraft is reduced. In one recent incident, a generator was loaded on board a C-17, and it leaked one to two gallons of fuel into the cargo compartment shortly after takeoff. To make matters worse, there was no spill kit on board the aircraft, and the loadmasters contained the fuel spill with blankets. When the aircraft reached its destination, the generator was off-loaded, and inspection of the unit revealed the following information:

· The fuel gage on the unit was inoperative, and the amount of fuel in the tank was unknown.
· Between 45 and 50 gallons of fuel was drained out of the generator.
· When the unit was loaded onto the aircraft, the fuel filler cap was oriented toward the back of the aircraft. The angle of the cargo deck during the initial climb out allowed fuel to flow out of the filler cap and into the cargo compartment.

This incident could have been prevented during shipping preparation by confirming the amount of fuel on board the generator. The inspector assumed the fuel gage was operational and accurate. A simple check of the fuel tank with a dipstick would have revealed the actual fuel level of the unit. If the equipment doesn't need to be used immediately after it is unloaded, consider shipping it with a lower fuel quantity to lower the risk of a fuel spill.

As we have become more environmentally friendly with our equipment designs, many of our units have vapor recovery lines that vent back to the fuel tank. On several occasions, these vent lines have returned fuel to the tank or began leaking as the pressure in the cabin decreased. Once the unit has been prepared to ship, it should not be run because the purged lines will re-fill and leak. In some cases, vehicles will be kept idling for a long period of time before they are loaded. This leads to a significant amount of fuel vapor being generated inside the tank. Before the vehicle is loaded, the fuel tank should be vented to the atmosphere outside the aircraft rather that have the vapors venting into the cargo compartment after takeoff.

My final concern is the accuracy of the CG markings on the equipment. In one instance, the CG marking on a piece of heavy equipment was changed after the equipment was loaded and the crew had entered crew rest. The next day, the loadmaster saw the changed marking and questioned its accuracy. As it turned out, the new marking was more accurate than the old one, but it was still incorrect--and if the aircraft had departed in that configuration, it would have had a five-degree aft CG, which is not where you want to be when taking off in a hot climate.

These problems are not limited to the USAF C-17 fleet. A small amount of time invested in the preparation of vehicles and powered ground equipment can significantly reduce the number of incidents of fumes in the cargo compartment. Here are some safety reminders:

1. Know the rules when you're prepping for cargo shipment.

2. If you're deploying equipment back from the AOR, ship it with the lowest amount of fuel permitted. Confirm the fuel levels with a physical measurement if possible.

3. Make sure the vapor recovery lines have been purged to keep them from venting as the aircraft ascends.

4. Pay attention to the CGs on vehicles and equipment you're loading. A quick reference book for the common types of vehicles and equipment would save time and help with load planning.

Generators and other flight equipment are loaded on to a C-17 Globemaster by members of the 92d Logistics Readiness Squadron at Grant County International Airport in Moses Lake, Wash.