They’re usually already open when the passengers arrive, so it’s just a matter of stepping up and into the cabin. And closing it? Well, that’s the pilot’s job. The door’s there to let you into the cabin—and that’s the extent of it, right?
Wrong. There’s no question that the cabin entry door exerts a kind of psychological influence on those about to board. Think of it: It’s the first thing that grabs a passenger’s focus as he or she approaches the airplane. It’s not at all like the influence the airplane’s overall looks, shape, and dimensions exerts. And those entering the cabin will have to deal with the door—and its steps, and perhaps the door latching mechanism—on a personal, hands-on level.
Those entering the cabin will have to deal with the door—and its steps, and perhaps the door latching mechanism—on a personal, hands-on level.In the feel-good, hierarchical world of cabin doors, the airstair door takes the prize. You can’t help but feel a sense of stature as you move up or down the steps of an airstair door. It evokes the news coverage you’d see of an arriving celebrity. Somehow, an airstair door boosts the spirit. It has large steps, sturdy handrails—and literally elevates your presence.
There’s a good reason why airplanes with airstairs are often said to have “ramp presence.” Translated, that means the fuselage stands tall on its more ample landing gear. You look up at it, sort of the way you’d look up at a monument. Of course, in the aeronautical engineering rulebook of tradeoffs, there’s a very good reason for that. The landing gear must be longer in order to give an airstair door enough room to extend. Or provide enough room for wing-mounted (jet) engines too, for that matter.
There can be other tradeoffs. When retracted, longer landing gear—especially those with a trailing-link design—take up valuable internal wing space. Space that might otherwise be used for additional fuel capacity. Obviously, this cuts into the airplane’s maximum potential range and endurance. Depending on the length of the airplane and the location of the main landing gear, the longer the nose—and the more forward the entry door—the greater the risk of a tail strike during a too-aggressive rotation during the takeoff run.
Other entry door considerations involve safety, which include the number and size of any handrails, lighting for the stairs, the pitch of the stairs, and the design and geometry of the door’s opening and closing levers and other mechanisms. The design also considers the safety of the stairs’ treadplates. You don’t want anyone slipping on the stairs or sliding off the edges. That means rubber or textured metal for a better grip, and side shields to prevent a foot slide. Those shields need to be wide enough to provide a gap that will let snow and water drain off the steps. So, a lot of thought should—hopefully—go into the door design. And the simpler the better, because the larger and more complicated the design, the heavier the door.
Never discount the importance of style and ambience. If a customer has put down millions for a turbine airplane, he or she has every reason for it to meet any and every expectation.Which brings up another topic: muscling the door open and closed. Springs and counterweight principles help a lot, but sometimes you need some extra help. Embraer’s Phenoms have an exterior grab handle for yanking the door down once you pull the latch to unlock the door’s securing pins. Earlier Phenoms didn’t have that grab handle; instead, the latch would open a horizontal slot to help you pull the door down. You’d reach up, put your hand in the slot, and pull. But danger could crop up when you close the door. Closing the latch also closes the slot. If your hand is still in the slot, your fingers could be pinched—or worse. That’s why there’s a placard warning of the danger.
What if your airplane sits lower on the ramp, and there’s no room for a proper airstair? That’s when you see the flip-down, ladder-style entry steps, or the truncated airstairs of the sort seen in earlier, entry-level Citations. No lighted steps, treadplates, or side shields here. They’re not as glamorous as full-blown airstairs, but they get the job done. But the ladder’s style means that you watch your feet as you make it up those three steps, and there may not be a handrail to help you along.
You say you fly a piston or turboprop twin? Well, that sort of rules out any forward entry door, because designers obviously don’t want you anywhere near propellers. Here’s where aft entry doors, like those used in the King Air series of turboprop twins, makes sense. To save weight, these doors drop down when their latches are released, and leather-covered straps instead of mechanical devices are used to raise and lower the door. A side benefit (?) is that with the door open, you’re in an ideal position to service the aft potty.
Wait a minute, I hear you say, what about the early Learjet and Piper Aerostar’s clamshell entry doors? True, these airplanes are “low riders” on the ramp, but wrangling a set of clamshell doors open and shut can be a challenge—and yes, if you’re a truly careless Aerostar pilot, word has it that it’s possible to risk losing a hand or arm if you choose to close them with engines running. At least, that’s the legend.
Want some more door lore? How about the Aero Commander/Rockwell Shrike and its turboprop stablemates, the Twin Commanders, which have their forward-hinged entry door right in front of the left engine’s propeller? You definitely want those shut before hitting the start switch.
Then there are the turboprop singles that are standouts in the door department: Pilatus’ PC–12s and Daher’s recent-model TBMs. (Pilatus’ PC–24 twinjet also has a humongous door.) They’re known as much for their big aft doors as they are for their other considerable capabilities. Talk about weight and mechanisms! Their top-hinged doors are so big that they use a pushbutton-activated motor for opening and closing. The door’s up and the motor’s failed, you say? Then reach up and grab a strap to pull it down. Even if you’re of normal height, you may have to jump up to snag the strap. If you’re on the short side, things can get entertaining.
All this stair talk may sound frivolous, but manufacturers pay a lot of attention to details like the ones discussed here, and more, such as door seals (inflatable or passive), water barriers (required to prevent water entering the cabin in a ditching), damping (you don’t want the door to slam down on its descent, you want a gentle landing), and door height (can’t have passengers skinning their scalps).
Much of this attention is safety-related, but never discount the importance of style and ambience. If a customer has put down millions for a turbine airplane, he or she has every reason for it to meet any and every expectation. Just ask Dassault Aviation. Pass through the doors of that company’s Falcon 6X, 8X, and upcoming 10X, and you’ll arrive in an entry hall, complete with a skylight. Now that’s a cabin entry experience you won’t forget.