THE “G” IS SILENT....

Acknowledgements: Thomas P. Turner, Mastery Flight Training, Inc. & Flight Instructor Hall of Fame inductee

Running the risk of once again focusing on a specific crash in my larger mission of using what people are talking about into positive LESSONS that will improve how they fly, here’s an excerpt from another recent NTSB preliminary report:

“... A retractable-gear Piper Turbo Saratoga was destroyed during a forced landing following a total loss of engine power while on approach ... The pilot/owner of the airplane was fatally injured. Visual meteorological conditions prevailed for the flight which originated about three hours earlier ... A representative from the fixed-base-operator at origin stated he serviced the airplane with 31 gallons of fuel, which filled the tanks. He further commented on the smoothness of the engine as the airplane approached the fuel pumps. 

The pilot informed the destination Tower that he was "lined up" for a straight-in landing to runway 14. The controller advised "cleared to land", which the pilot acknowledged. Approximately 1.5 minutes later, the pilot advised "I've lost power." The controller asked the pilot if he thought the airplane would reach the runway, and the pilot responded "Yes." Soon after, the pilot advised "I'm not going to make it, I'm in the trees." There were no further communications .... The airplane collided with trees and terrain, aligned with runway 14, about 1.5 miles prior to the landing threshold. 

The pilot held a private pilot certificate with a rating for airplane single engine landing ... and had flight experience of 450 hours in the accident airplane make and model. The airplane’s most recent annual inspection was completed February 19, 2019 ....

 The fuel selector control lever was observed near the right fuel tank position. However, examination of the fuel selector valve revealed the selector plate was out of the detent and not fully seated in the right fuel tank position. Further examination of the selector valve revealed its lever was seized in position. Upon dissembly, the selector plate indicated an intermediate selector valve position. During dissembly, when the selector valve could be rotated and was placed in the left or right fuel tank position detent, it was noted that the associated ports were unobstructed. 

I often tell pilots in my type-specific presentations that there are two questions I cannot answer about their airplanes: (1) Why did the manufacturer do this, and (2) Why didn’t they do that? My point: I can’t change the way the airplane is designed. My job is to explain how to work with the aircraft as it exists.

Why is this relevant to the topic introduced by the NTSB preliminary report above? With few exceptions, light airplanes require active management of the fuel system in the form of manually switching from one tank to another. There is no “BOTH” fuel tanks position for virtually all of us folks flying singles. 

In airplanes requiring fuel tank selection, checklists and good operating practice call for landing with the fullest tank selected. This is designed to prevent fuel starvation if uncoordinated flight or running a tank completely dry causes a power interruption close to the ground, where there may not be enough altitude … and therefore time … to switch to another tank and get the engine restarted. 

 But when should the pilot make this final tank selection? The NTSB records show a clear record of fuel starvation crashes if this final tank switch is done close to the ground. The answer, then, is to switch tanks higher up. I suggest making the final tank selection at the point you begin your descent from cruising altitude toward your planned destination. You must plan your cruise fuel burn so you have enough fuel in that final tank to descend from cruise, manoeuvre for the pattern or for the approach, actually fly the instrument or visual approach, go around or fly the missed approach procedure if needed, and climb back to a safe altitude well above the ground — all without switching tanks after Top of Descent (TOD). 

 ....  In fixed-gear airplanes tank selection is usually considered to be a “Before Landing” checklist item, done in the pattern or close in on a straight-in approach. 

 In retractable gear airplanes it’s common to include tank selection in the ubiquitous GUMP check — the acronym standing for Gas, Undercarriage, Mixture, Propeller ... When do you perform the GUMP check? Most instructors teach it’s when you’re cleared to land at a tower-controlled airport, or on downwind or final approach course inbound. The common link: most retractable gear pilots go through the GUMP check when they extend the landing gear. 

 Most of the time ... (in both aircraft types) ... that’s too close to the ground to safely make a fuel tank selection. 

 Reading the NTSB report used as our example, where a mechanical malfunction appears to have made switching to the right fuel tank difficult or impossible and may even have prevented him from returning the selector to the left tank when the engine stopped, the report of engine failure came very soon after the pilot was cleared to land — at a point in the pilot’s approach near where he was likely to have extended his landing gear.

Pilots frequently voice the GUMP check when I fly with them as their instructor. I strongly advise them against actually switching tanks at the point they use the mnemonic. Most of the time they reply that when they use the G in GUMP, they are merely verifying that the fullest tank is selected. 

That’s fine, but in debrief I ask: If you find the fullest tank is not selected at that point, what do you do? Do you violate good operating practice and risk engine failure close to the ground by switching tanks to rectify that deviation? Do you break off the approach and climb to a higher altitude to switch tanks, then resume your approach? Or do you leave the fuel selector where it is, rendering the check of tank selection moot? 

The purpose of the GUMP check is, more than anything else, as a reminder to extend and confirm extension of the retractable landing gear .... and I don’t want to discourage the use of any mnemonic that reduces the chances of a gear-up landing ... From a practical standpoint, however, in the standard GUMP check THE G IS SILENT. There’s nothing you should do with the fuel selector at the point most pilots use the GUMP check. Instead, final fuel tank selection should happen at Top of Descent, with sufficient fuel in that tank to complete the landing and even climb back to altitude without further tank selection.

FLY SAFE!