Safeguarding the “Gotcha’s”

Safeguarding the “Gotcha’s”

Safeguarding the “Gotcha’s”

Every aircraft has its unique characteristics, which begs the question: how can this airplane hurt us?

It is a short trip today: Seattle’s Boeing Field (KBFI) to Boise, Idaho KBOI) in a vintage 1983 Lear 35. Less than 30 seconds after our wheels leave the pavement of runway 13R we are doing 250 knots and climbing at 4,000 feet per minute. With the power rapidly being reduced to 65 percent, we come whipping up to the Kent Seven departure procedure’s climb limit of 2,000 feet. The airplane really wants to keep going up, but Seattle Departure Control has their frequency clogged with airline traffic leaving from SEATAC, which is just off to our right, and we can’t get in a word edgewise. So, we roar along at 2,000 feet doing 250 knots, burning $8 worth of fuel every 15 seconds, and heading 90 degrees away from where we really want to go, with the little airplane champing at the bit like a racehorse held back at the track.

Despite all this fuel-thirsty, thoroughbred performance, and contrary to what you may have heard, Learjets are quite easy to fly. They have nicely balanced controls, go exactly where you point them, and have fighter-like acceleration and climb rates. It is hard to believe they were originally designed back in the early 1960s when most of us were still in high school or college. And yet, although the older models will do just about everything newer versions of the airplane will do, they have a reputation among pilots for some peculiar, mostly “age of design”-related operational issues, many of which can be fatal if you do not pay careful attention. In the vernacular of pilots, these become known as “gotcha’s.”

The Learjet 35 contains its fuel in two tip tanks, two wing tanks and an aft fuselage tank. The fueling process requires special care that one tip tank is not filled while the other remains empty.

Avoiding the Gas Gaffe

Well before you board the aircraft, the Lear 35 “gotchas” start with the fuel system. The big TFE731 fanjets on these little airplanes each put out 3,500 pounds of thrust and use so much fuel that the engineers had trouble finding places to put it all. Just over 900 gallons can be boarded, and it is stashed all over the place. There is the equivalent of seven 50-gallon drums (1,175 pounds or 172 gallons on each side) in the wing tip tanks.

Inboard of each tip tank, squeezed into each of the small thin wings, there is another 1,254 pounds (a bit over 180 gallons a side). Finally, behind the baggage area aft of the rear passenger seat, there is a tank the size of a cattle watering trough called “the trunk,” which holds another 1,340 pounds or just under 200 gallons. The little jet, which has a basic operating weight of 10,700 pounds, takes off with just under 7,000 pounds of fuel on board.

With tanks scattered all over the airplane, filling them safely becomes a procedure that the pilots pay careful attention to. Unlike newer business jets, which nearly all have single-point refueling, the only way to fuel a Lear 35 is via the fuel ports in each tip tank where it flows by gravity into the wing tank on the same side. You must watch that the line guys do not fill up one tip tank while the other is empty, as that will cause a fuel imbalance of over half ton. Given the relatively narrowly spaced landing gear, this will tip the airplane literally up on its side. In addition, there is no way to place fuel into the fuselage or “trunk” tank from outside the aircraft. That tank can only be filled by transferring fuel from the wing and tip tanks via on board electric fuel pumps. It’s a time-consuming activity that usually requires the aircraft be powered up, and is normally done before landing or as the airplane taxis in.

After the line guys are done filling the tip and wing tanks, you absolutely must check each of the fuel caps for security. There is just one on each side, they look almost identical to those on a Cessna 310, lie on the outboard side of the tip tank and so cannot be seen from inside the airplane. If the left is less than fully fastened, they can depart the aircraft in flight, which will cause all the fuel on that side (literally a ton), to be completely siphoned out into the slipstream within a period of minutes. This in turn will cause the engine on that side to fail, and creates a lateral 2,400-pound fuel imbalance that makes the aircraft non-controllable around the horizontal axis. This “gotcha” is this reason you will find at least one of the pilots of a good Lear crew to be physically present during any fueling, and even after that, at least one of them will walk around the airplane and literally touch each of the two fuel caps before boarding. Personally, I check them twice.

Close the Door Already!

While still on the ground, the next “gotcha” with potentially fatal consequences is the cabin door closing mechanism. The complex process required to close the door has more steps than that needed to start the engines. Screw it up and a loss of pressurization could occur, which at the altitudes at which the airplane is capable of operating could easily prove fatal.

The process begins with pulling the lower half door up to a temporary lock position using a T handle attached to a cable, while the upper half is still open. The lower door is then locked in place with a rotary handle, then the upper half pulled down. One then activates a hook driven by an electric motor contained within the lower door itself, to cinch down the upper door. The motor is controlled by a small, very hard-to-find toggle switch lost in the upholstery, located on the forward side of the lower entry door. Looking lost and muttering under your breath while you are groping for the switch, does not enhance the image of your piloting skills to the two pax sitting less than 4 feet away.

Once the doors are cinched together by the electrically powered hook, the upper door handle can be thrown over into the fully locked position. The electric motorized hook, however, is still holding the door fast, which would make exit during an emergency evacuation impossible. Thus, the next step is to reverse the hook’s motor, in the process disconnecting the hook entirely. The final step is to call out “door closed,” while your buddy sitting in the cockpit with the master switch on checks to make sure the “door” annunciator panel light has gone out, at which time he says, “light out.” Miss a single step and the light remains on, which causes the passengers to wonder just how good of a crew you are, if you can’t even figure out how to close the door. Luckily, we know the drill, so with the door now closed, the engines are started, which is a relatively simple task.

Stay Out of the Grass

Now it is time to taxi the aircraft and another potentially embarrassing “gotcha” presents itself: the nose-wheel steering. This system is operated through the rudder pedals, but is electrically driven by a motor that has variable authority depending upon aircraft speed. From a practical point of view, this means that the pilot (at least until very familiar with the airplane), can never quite tell how much the nose wheel will turn for a given amount of rudder pedal movement. In addition, small inputs to the rudder pedals result in the system making a squealing sound similar to that of a pig being castrated, which in all its unpleasantness is clearly audible to the passengers.

All this has many new Lear 35 pilots lurching down the taxiway, with the repeated odd noise clearly announcing to the passengers that the pilot must be new to this aircraft. This continues through the initial part of the takeoff run, when at 45 knots the nose-wheel steering becomes dangerously sensitive so it is turned off via a red button on the control wheel.

The CRM drill to prevent an off-runway excursion “gotcha,” goes like this: Pilot flying (PF) advances the throttles PNF calls “power set,” then at about 45 knots “airspeed alive,” at which time PF presses the red button on the control wheel and calls out, “nose wheel steering off.” On landing, serious accidents have occurred if the nose-wheel steering is “ON” at touch down because even a small amount of rudder input (say, a slight slip for crosswind purposes) will move the nose wheel well off center. Thus, when it meets the pavement, the nose wheel immediately points the airplane toward the grass. For this reason, the nose wheel steering is left OFF on landing, and kept that way until the airplane is well slowed down, something that is not at all intuitive.

The partially-hidden toggle switch (pictured at right) operates an electrically operated hook that latches the clamshell door together (above). Not following proper door-closing procedure will lead to a potentially dangerous “gotcha.”

Old School TOLD Calculations

Nearing the runway and ready to fly, the next potential “gotcha” is the need to use TOLD (takeoff and landing data) cards. In newer jets, this information is automatically calculated by the onboard computer, and moved to the PFD (primary flight display), but this convenience is not available on the older Lear 35s. Pilots must look up the required speeds (V1, Vr, and V2), runway length, and power settings for each takeoff. The numbers are dependent upon temperature, weight, runway condition and elevation.

Most of us have made up charts for the common numbers, and pasted them to the checklist, but it still can be tricky. For example, for Boise today, (elevation 2,871 feet), the readily available chart is not valid because it is for sea level operations only, so a larger book is consulted for the numbers applicable to that elevation. Usually the charts in the larger book never show the exact altitude and temperature you are at, and so some extrapolation is required.

Once the takeoff or landing information has been extracted from the charts, to make it readily apparent to the crew it is hand printed on a TOLD card and stuck somewhere obvious for both pilots to see.

A Gotcha-Free Landing

While the flight decks in newer jets can perform the takeoff data calculations, the Learjet 35 requires the pilot to acquire
and display the data the old-school way.

We have been blasting along at 2,000 feet and 250 knots on our BFI departure for several minutes when we finally get a word in edgewise with Seattle Departure and are given a left turn and climb to 12,000 feet. We arrive there in less than three minutes and meet with our next “gotcha.” Most of these older Lears do not have altitude preselect on either the flight director or the autopilot. As a result, both pilots need to be fully alert during the climb, because when doing 4,000 feet per minute, with the usual “1,000 feet to go” CRM call out, you have less than 15 seconds to get the climb rate under control or an altitude bust is almost a certainty.

Luckily, on our flight to Boise today, we nail the altitude, and with fuel caps staying in place and the cabin door remaining closed, we do just fine as we climb to FL390 to happily discover a 100-knot tail wind. Twenty minutes later we are at the TOD (top of descent) for our approach into Boise. During the decent we dial up the local ATIS, then look up the TOLD numbers for the airplanes weight, plus temperature and altitude of the airport. We make a good landing being sure the nose wheel steering remains turned off. We turn the nose wheel steering on as we exit the high-speed turnoff, and while taxiing to the FBO have the foresight to transfer fuel from the wing to the “trunk” tank in the aft fuselage.

Forty-eight minutes after leaving BFI, and having luckily avoided all the “gotcha’s,” we park the airplane on the ramp at BOI, borrow a crew car and head out for breakfast thinking, “What great airplanes those Lear 35s.”

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