It’s All About the APU

It’s All About the APU

It’s All About the APU

It is 8 degrees Fahrenheit on the ground in Lincoln, Nebraska with ice and snow on the ramp, and a nasty wind blowing down from somewhere near the Arctic circle. Having just arrived by airline, fellow Lear pilot Tim and I are cautiously slipping and sliding our way across the icy ramp to the FBO hangar where there is a Lear 45 awaiting us. One of the companies we fly for recently purchased this Lear to replace their old Lear 35 (see “Old Dogs & Old Airplanes,” T&T, October 2018). Assuming we don’t freeze to death first, we are going to fly it home later in the afternoon. 

A Lear 45 is almost identical to the model 40 we commonly fly except it is four feet longer and has two additional passenger seats (for a total of nine). The airplanes also have a common type rating, which is an advantage in that it makes pilot scheduling easier and training costs much lower. But, the real benefit of the 45 for us is that it has an APU (auxiliary power unit), which as we stand shivering at the FBO’s frigid entrance door, is something we think will make our cold weather operations much more comfortable, particularly to isolated parts of Alaska. 

When getting in a new-to-you airplane, it is helpful to note any well-worn switches and signage (like the APU ones seen here).

Just as we get done stomping the snow off our shoes, the FBO’s office door is opened by the airplane’s salesman. He is a friendly fellow wearing jeans and has a somewhat scraggly long grey beard, all of which strikes me as rather odd for a business jet sales guy – most of whom look like they shave twice a day and dress in dark suits with white shirts and ties. But hirsute appearance notwithstanding, he gives us a big smile, welcomes us to Nebraska and invites us into the warm room where fresh hot coffee awaits. He says our airplane is out in the hangar ready to go and asks if we would like to the line crew to pull it outside. To someone from the Pacific Northwest where the weather, by comparison, is just plain balmy, that seems like a funny question. The idea of a pre-flight out in the snow and freezing cold is not at all appealing, and something we are not well-practiced.

Upon hearing this, our new bearded friend takes us out into a very large hangar with a clean white floor and five other business jets in various stages of repair scattered about. It feels like 80 degrees, and I cannot help but note the space has some very large natural gas-fired radiant heaters hanging down from the ceiling, which are roaring away like a jet engine afterburner. We see our “new to us” airplane parked in the corner under one of the radiant heaters, and a couple of technicians with polishing rags still in hand doing the finishing touches. They have it so shiny that when I get closer, I can see my face mirrored in the paint.

Tim and I begin our pre-flight, and other than the extra feet of fuselage length, find little difference between this airplane and the Lear 40 we left back at home base. Entering the cockpit to look over the gauges and switches, I can see the white lettering and switches on the APU control panel on the center console are almost worn off, whereas those of the HF radio control panel look brand new. Years ago, an old airline pilot told me that when getting in a new (to you) airplane, pay particular attention to the location of switches and signage that is well worn because those are the ones previous pilots have used a lot and you probably will too.

Finally, after spending nearly an hour carefully going over the airplane and making extra sure the air intake and exhaust for the APU are clear, we tell the line guys they can pull the airplane out when they are ready. This turns out to be a complex process because several other airplanes are in the way and need to be moved first, during which the hangar door is open with heat escaping at a prodigious rate, and snow blowing in making everything wet. But the line guys, decked out in fur hats with ear muffs, thick down coats and snow boots take it all in stride and soon have our airplane outside.

We promptly board the airplane and quickly close the two-section door before all the heat escapes, then get involved starting our new toy, the APU. This $200,000 extra piece of airborne equipment is little jet engine about the size of a five-gallon paint bucket, which is mounted in the tail section with an air intake on the top aft fuselage and a jet exhaust opening on the right side just above the engine pylon. It puts out enough energy to nicely heat the cabin and makes starting the engines much easier. I push the APU’s start switch and the little turbine cranks up right away, then engage the “pack” switch that controls the heating. Shortly thereafter, it is noisily blasting out hot air into the cabin at a phenomenal rate. Ah, very nice indeed. In this weather, definitively worth the price. 

The line guys then come out with fresh coffee for the small galley, and we spend four to five minutes fiddling with the tanks. It turns out the Lear 45 has a heated container for coffee and an identical one next to it for hot water, which is a well thought out system as not all passengers like drinking FBO coffee. When that task is completed, plus some lunches boarded, we complete the checklist all the way down to the “engine start” section. Then while basking in hot air from the APU and sipping coffee, we relax and wait for our single passenger (one of the airplane owners) to show up.

After sitting awhile, with the snow drifting down on the airplane, we start thinking if we stay put here much longer, we will need to get the airplane de-iced. You have to be careful when you pull a warm airplane out of a heated hangar and park it out in the snow, as the snow can melt on the warm wing surface, then re-freeze, often being hard to see. Although there is a de-ice truck parked nearby, we would rather not use it as it is very expensive, probably between $750 and $1,000. It would also leave a messy film of deicing fluid all over our nicely polished “new” airplane. While we are debating our options in this regard, our passenger shows up, helps himself to coffee and settles in one of the very comfortable leather passenger seats.

Tim and l look at each other trying to figure out who will be the lucky one to exit the aircraft and inspect for ice. Unfortunately, I have a hat and he doesn’t, which becomes the determining factor. I climb back out in the blowing snow, do a careful walk around and not finding any worrisome ice, I jump back in and quickly close the door.

With the APU running, the engine starters each promptly light up in spite of the fact the intakes are not facing into the prevailing wind as you would normally want them to be. Once everything is running, we shut down the APU, get our IFR clearance and notify ground control we would like to minimize any ground delay due to potential ice accumulation. She seems to be well versed with this issue and immediately clears us to Runway 35 via the nearby Alpha taxiway. We roll down the taxiway working our way through the pre-takeoff checklist, finding that some switches are not where we expect them to be. It also turns out that the FMS in this particular airplane will not automatically calculate take-off speeds, which sends us scrambling into the flight manual behind the seat. 

While we are doing this, the helpful controller in the tower calls while we are still on the ground control frequency and clears us for takeoff, but adds that there is inbound airline traffic some five miles out – her polite way of saying “hurry it up.” Yikes, professional pilots as a matter of training and habit avoid situations where they feel rushed, but that is how we are starting to feel. Luckily, with two people in the front, we get the numbers out of the book and complete the “line up” checklist just as we pull the airplane onto the runway. We stop there for five seconds making sure we have completed everything then add power. 

With the airplane light, the conditions cold and the wind blowing straight down the runway at 25 knots, acceleration through V1 and Vr is almost immediate. Following our departure clearance, we make a 50-degree turn heading 300 and are in the clouds and snow climbing through 10,000 feet at more than 4,000 fpm when we are switched to the center frequency. In reply to our first call, the center controller immediately clears us to FL410 and direct to KBVS – some 1,300 nm to the west. When we activate the NAV switch on the autopilot/FMS control panel, the airplane makes a 3-degree turn to the right to compensate for winds that are slightly from the north then heads straight for home. What a pleasant surprise, weather factors aside, that there are some real advantages to flying in the Midwest. That kind of clearance would be a true rarity in the LA Basin.

Twenty minutes later, we are at FL410 and notice that the ball on the turn coordinator is slightly to the left when the wings are level. We fool around with the rudder trim but cannot fix it without causing the airplane to with one fly wing down slightly. It seems the airplane is somewhat out of rig, and make a note to have that looked into later. We next notice the airplane has a slight wing wag, going 3 to 4 degrees to the left or right in about 15-second intervals. Sometimes this can happen when on NAV as the system is seeking the centerline of the GPS course, so we switch the autopilot mode to HDG, yet it still continues. We decide it must be something to do with the yaw dampener and add that problem to the list. Other than these minor issues, our “new” airplane flies like a champ.

An hour later, I go back to visit the small bathroom and get some lunch. In the process, I chat with our passenger, who was the decision-maker in the aircraft purchase. We review not only the airplane’s useful load, fuel burn and range but also mundane things such as the seat controls, leather interior, lighting and phone capability. But more than anything else, what he really likes is how the APU had the cabin toasty warm and well-lighted when he first arrived. I think to myself, no wonder it is those switches that are so worn.

Three hours later, we are 50 nm east of the Cascade Crest with the TOD (top of descent) showing up on the panel- mounted map. The power comes all the way back, and we start down at 350 knots indicated and 2,500 fpm. We are still a bit fast when arriving over the IAF, so we switch off the autopilot, manually pitch up slightly to slow down, then trigger the gear at 200 and full flaps at 150. Four feet longer or not, the 45 on approach behaves just like its little brother, the 40, and we make a smooth landing without any issues. Taxiing to our home FBO, it is not really that cold but we cannot resist starting up the APU anyway. Tim and I tell each other the ostensible reason for doing so is to keep the cabin heated and all the interior lights on so our passenger can comfortably disembark. But sure, the real reason is we want everyone to hear that little jet engine whining back there, with the smell of burnt jet fuel wafting about after we pull up to the ramp and shut the engines down. 

The truth of the matter is a noisy little APU wailing away when the airplane is otherwise quietly parked on the ramp is a pilot status symbol. The noise itself is probably worth the whole airplane purchase, let alone the cabin pre-heating. 

About the Author

Leave a Reply