Once in a while I am asked a question like “What was your scariest flying experience?”. Usually I am at a loss for an answer because flight planning is as much about the worst case scenario as itis about what you actually intend to do. Hopefully the decisions about what to do when things go wrong were made on the ground before walking to the airplane, and, if necessary, you just do it. Over the years, however, one common theme has emerged that always gets my heart going and it can be expressed in two words: Low Fuel.
I have three or four such stories, and the Air Force T-37 story I am leading up to will be the first one that I have written down. This one was a little tougher to articulate because it involves nuances of restricted airspace and aircraft systems that are important to the story. Low fuel is like imminent engine failure, except worse. In aviation, while we try to account for every possible malfunction, including engine failure, we don’t spend a lot of time planning for
multiple failures. This is because much effort has gone into creating reliable systems, and history has proven that we can cope by having a plan that relies on redundant systems to accomplish a safe landing after a significant malfunction. In the rare case when multiple failures occur, we must rely on our experience and systems knowledge to muddle through, because our checklists cannot account for every combination of circumstances. As a back-up to engine failure, single-engine civilian airplanes must be able to fly slowly enough to land in a typical field (stall speed no higher than 61 knots per FAA) Single-engine military jets have ejection seats. Twin-engine airplanes
will generally fly all day on one engine, and if one fails, the regulations require us to land at the nearest suitable airport (in point of time).
Fuel exhaustion is like losing all your engines at once. To avoid it, regulations require us to land with ½ hour of fuel onboard, or more. We must plan for that and constantly compare our fuel burn against the plan throughout the flight. So being caught low on fuel happens when something catches you by surprise. Examples would be a system malfunction, a change in weather, or
unforeseen airport closure. If necessary, a pilot can declare an emergency and obtain straight-line routing to the nearest suitable airport. But if that routing is right through restricted airspace, and the low fuel state is somehow your fault, playing the emergency card, while safest, can be a risky
career move for a young Air Force officer. This is a story about that.
As a digression, I will mention that my first assignment out of pilot training was as a copilot in a KC-135, a Boeing 707 used for in-flight refueling, and my very first unsupervised flight as a line co-pilot was with a young aircraft commander with a hard-to-pronounce Greek name. Together, on that flight, we experienced an abnormal indication. The light indicated low oil pressure on one of our four engines. I dutifully got into the checklist and determined that we would not have to shut it down because the redundant gauge was indicating normal pressure, meaning that the light was just a faulty indication.
The reason I mention this story is because approximately four years later I was paired with this same pilot with the Greek name. We were both, by coincidence, re-assigned to instruct student pilots in T-37s at Sheppard Air Force Base in . There was a normal break in training on the weekends and a taxpayer-funded perk allowed instructors to fly cross-country to wherever they wanted to go, and I was trying to get to my sister’s wedding.
I will now jump right to the moment of surprise by saying that we were at cruise altitude when a red “low fuel” warning light came on. Normally, when that light came on, it didn’t mean simply low fuel, it meant very low fuel. I guess I should admit to you that we had been looking at a yellow caution light for most of the flight because of a malfunction that seemed harmless to us. Let me explain.
The T-37 was designed to fly upside-down. In fact, this was an era when some European Air Force aerobatic teams (Thunderbird counter-parts) were performing air-shows with them. Going to work every day to teach aerobatics in a T-37 was a thrill that routinely put roller-coasters to shame, but I am digressing again. The fuel system on the aircraft was designed with a fairly
simple combination of pumps and float switches to assure positive fuel flow for up to 30 seconds during inverted flight (more correctly, negative-G flight). The system would pump fuel from the wing tanks to the center tank and automatically keep the center tank between approximately 75% and 100% full. Fuel to engines was always supplied directly from the center tank. If the fuel level in the center tank went below 75% a yellow caution light would come on and the only three things that could cause the yellow light to come on were:
A bad pump, failing to move the fuel from the wings.
A bad float switch, failing to tell the pump to operate.
Empty wing tanks; the design would normally empty them first.
Empty wing tanks could be ruled out if the yellow caution light came on early in the flight and total fuel exceeded the center tank capacity, as it did with us that day. The solution for any malfunction was simply to move a guarded switch to the “gravity feed” position. This would disable the pump and allow ample fuel-flow to the engines as long as we avoided inverted flight. If
this was like any other training flight, we would have been expected to land as a precaution and get it fixed, but after a brief discussion we agreed about the harmlessness of continuing in “gravity feed” and we pressed on towards my sister’s wedding. That decision left us exposed to the laws of unintended consequences, and we were about to learn our lesson. The instant we decided to continue with the switch in the “harmless” gravity feed position we had sold our souls to the underworld of system surprises. While the operating manual assured that all the fuel was usable, we were still heading into the realm of the unknown in this abnormal configuration, against policy. Any subsequent glitch that could be traced to that decision would be incriminating for both of us. It was normal to see a yellow caution light late in a flight after all fuel had been pumped out of the wings, so we were quite comfortable staring at it for most of this flight. Furthermore, for a Lieutenant logging maximum flight time to improve his chances to transition to the airlines, the
red “low fuel” warning light was not unheard of either. Sometimes we would practice landings until this light came on, but never far from the runway. In an airplane, red means bad. We nicknamed this the “mission complete light” because it only came on when the fuel in that tank was down to, I forget exactly what number, maybe 40 gallons of fuel. This translated to about the 35 minutes of fuel left. If this light came on, even on final approach, any landing delay would be serious cause for concern.
But the red light was on. And we were way too far from our destination, Eglin Air Force Base, to be this low on fuel. I got real concerned and told the Greek guy that I wanted to declare an emergency and cut right through the military restricted areas that surround Eglin. This would have disrupted all military operations in an area the size of a small state, meaning certain trouble for
both of us. I could see him counting the reasons in his head. Somewhere an Air Force General would demand answers, then probably another General, then a Colonel, then another Colonel, etc., until someday soon we would be on the carpet in front of one of them explaining why dozens of military aircraft were diverted and unable to complete their missions because of my sister’s
wedding.. But, in my mind, we were about to run out of gas, which was worse?
So, there we were, miles from our destination with the red low fuel light on. Never mind that the total fuel indicated much more than the red light was suggesting; my mind went immediately to the worst case scenario, that we were nearly 30 minutes away from landing with maybe 30 minutes of usable fuel before flame-out. When the Greek guy did not agree to cut across the
restricted areas, I urged him to tell me why he thought we had an option! I have learned the importance of putting your finger on the issue and verbalizing it in a crew scenario, I pressed him to tell me what he was thinking, how could this be anything besides a very low center tank? This
was the tank through which all fuel flowed on its way to the two engines, and it was low on fuel! He pointed to the gauge showing a higher total quantity. My counter-point was: what if some of it is trapped? He shook his head to that notion and said there was probably some other explanation. He did have a point that the gauge was indicating twice as much fuel as the warning light
suggested, and I could not think of anything that might trap the fuel in the wing tanks. Also a malfunctioning pump/float switch seemed too unrelated to trapped fuel and too much of a coincidence. So, in the end I deferred to the more senior Greek guy, knowing that in the worse case scenario we still had the “canopy-1 letdown” (slang for ejection seat).
As we proceeded along our planned route, I watched the fuel in all tanks decreasing evenly and became more convinced that he was right. We landed at Eglin with our planned arrival fuel and I attended my sister’s wedding as planned. The next chance I had to look at my operating manual I found a note that explained everything; I even had it highlighted!. It said something like “ Note: When selecting “gravity feed” all tank quantities will decrease together and possibly cause the low fuel light to illuminate at a higher total fuel”. I thought I knew that book pretty well up to that point, but had never thought enough about what this paragraph was trying to tell me. If there is any moral to this story, it is that a pilot needs to stick to the book no matter how well
he thinks he understands an abnormal situation. If you do that the boss will back you no matter what happens next. One of the easiest decisions in aviation is to eject out of a burning airplane, but many pilots have ridden an airplane into the ground trying to save it after they have broken some rule. If your ego hungers for the opportunity to make impressive decisions don’t worry, there will be plenty of situations that the book does not cover. But the minute you defy policy, your supporters will scurry from you like proverbial roaches when the kitchen light is turned on.
Captain’s Log 