Juggling the numbers
Pilatus’ home base
A view from a Citation M2 shows the Pilatus factory, tucked against the hillside at the far right. To get to the runways, airplanes must cross a public road.
Where: Buochs Airport (LSZC), Stans, Switzerland
Photographer: Peter Herr, Textron Aviation
Each airplane has a different empty weight. But what is empty weight? There are many definitions to choose from. There’s standard empty weight (no frills or options), basic empty weight (an airplane with all its equipment, but no pilots), empty operating weight, and basic operating weight (the airplane’s basic empty weight plus the weight of the crew and their flying gear, along with any unusable fluids). Basic operating weight will always be higher than the standard or basic empty weight, so anyone looking at an airplane’s standard empty or basic empty weight—as represented in advertisements, for example—should understand that the airplane may in fact have a misleading, lower-than-published payload. That means fewer passengers and smaller maximum fuel loads. That, in turn, means less range.
Which brings up full-fuel payload. Most turbine-airplane mission profiles require that fuel weight be traded against payload, hence partial fuel loads are the rule. But if it’s range you need, then the temptation is to top off the tanks. The trouble is, an airplane’s payload will suffer dramatically. You may be limited to yourself and maybe one passenger.
When visiting Piper to fly the M600 featured in this issue, we learned that basic empty weights and full-fuel payloads vary. Because of avionics and other options, basic empty weight was 3,633 pounds for one airplane, 3,650 pounds for another, and 3,735 pounds for yet another brand-new M600. Full-fuel payloads came in at 578 pounds, 610 pounds, and 658 pounds. But at one point Piper published full-fuel payloads as an unwavering 700 pounds. That may change.
Discrepancies among individual airplane weights are not limited to the M600, of course. The M600’s new GFC 710 autopilot may not need to be disconnected in order to perform coupled missed approaches, but the M600, like all other airplanes, is still subject to the laws of physics. Check your airplane flight manual for your airplane’s true weights, and know that airplane design is always a tradeoff between weight, structural limitations, and performance.
Which brings up cruise speed and fuel burns. But that’s a subject for another time. —Thomas A. Horne, Turbine Pilot Editor
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