Not Deadly -- But Costly

Gear-up accidents and how to avoid them

April 1, 2005

Ask experienced pilots of complex aircraft what they fear most as far as accidents go, and you likely won't hear about obvious crises such as an engine failure or a loss of control on an instrument approach. No, the most competent, careful pilots I know — to a one — say, "I'm afraid of landing gear up."

Why would a normally nonfatal event — many gear-ups don't even qualify as accidents — strike fear into the hearts of skilled, high-time pilots? Because they know it's one that only takes a couple-minutes lapse of attention, or distraction, or misunderstanding to cause. Those pilots who admit they are human know we all experience such moments.

The effects of distraction

The pilot of a V-tail Beechcraft Bonanza was practicing an instrument approach, presumably without being under the hood, as the accident report lists no other occupant in the airplane who might have acted as safety pilot. As he flew down the glideslope toward the runway, he was distracted by two airplanes that overflew the runway's threshold at about 1,000 feet agl and two helicopters hovering over the taxiway next to the runway. So focused was he on this other traffic that he neglected to lower the gear.

The fact that the traffic pattern is busy can be distracting, but this is the normal state of affairs at many airports. Distraction brought on by other aircraft ranks high in the reasons pilots give for neglecting to put down the gear.

Focusing on procedures other than those listed on a before-landing checklist — such as flying an instrument approach or absorbing information from various avionics — can also distract pilots. A change in clearance or runway busts some, while an unexpected wind situation confounds others.

Mindset

A commercial pilot was practicing instrument approaches (again solo — maybe this isn't such a great idea) in his Cessna P210 at Boise Air Terminal/Gowen Field, in Boise, Idaho, on a May morning. On his second approach, he reported that "at the last minute on the second approach I was cleared for a touch and go. The best way I can describe it, I was still in an 'instrument- approach mindset' and failed to lower the gear."

When asked if he had heard the gear warning horn prior to impact, he replied that he didn't know there was one, and that he had not performed the before-landing checklist.

Danger! Warning systems

Like the P210, retractable-gear aircraft certified under Part 23 are required to have a gear warning system that comes on when the throttle(s) are pulled back beyond a setting normally used for a landing approach and the gear is not fully extended and locked. Gear horns in contemporary retracts are typically intermittent instead of continuous to avoid confusion with the stall warning horn — although pilots do manage to mix them up in high-workload or particularly stressful situations. Or in seemingly benign ones.

The pilot of a Beechcraft Baron landed gear up at the G.V. Montgomery Airport in Forest, Mississippi, after a 45-minute flight. Although his usual technique was to reduce manifold pressure to 15 inches, set 15 degrees of flaps, and "at the same time lower the landing gear" while approaching downwind, he failed to follow through. He noticed that the airplane didn't slow down like it normally did, so he extended the flaps fully. He held 15 inches of manifold pressure all the way down final, finally pulling back the throttles just prior to the flare, at which point the landing-gear warning horn sounded. He said his mind was "stuck on airspeed," according to the report, "and he immediately thought it was the stall warning horn, and lowered the nose a little.... Once he had the airplane level going down the runway he remembered thinking that it didn't matter if it stalled and he just kept holding it off and bleeding off airspeed." Only when the grinding noise began did he finally think of the gear.

While most retractable aircraft conform to the standards under Part 23, pilots of classic, kitbuilt, or experimental aircraft need to pay particular attention to learning the gear-extension and warning systems in their aircraft in order to avoid the dreaded gear-up landing.

Gear warning — or not

I can imagine a scenario where a Cessna 182RG has picked up a load of ice — inadvertently, of course — and the pilot must use power throughout the final approach to landing. Because of concerns of a tailplane stall or change in the flying characteristics of the wing, the pilot also leaves the flaps retracted. Both actions short-circuit the landing-gear warning system on the 182RG, which is actuated by a throttle position equating to 12 inches and a flap setting of 25 degrees with the gear retracted. The pilot, distracted by the prospect of an iced-up landing and focused by the desire to keep the airplane flying, fails to extend the gear. While the airplane reaches the runway safely, the consequence of distraction and tunnel vision is a gear-up slide on the pavement. If you need yet another reason not to probe possible icing conditions, here's a fine one.

The 'fail-safe' gear

Manufacturers are really trying to help us here, and in distinguishing their aircraft from others have innovated several ways to keep pilots from landing gear up (aside from welding the gear in place).

Perhaps the best known is the automatic gear extension feature on early Piper Arrows, Lances, and retract Saratogas. Since a large portion of the accident exposure is to the new retract pilot, it makes sense that Piper, in developing step-up airplanes from its popular Cherokee series, would seek to assist pilots should they fail to put the gear down by the time the airplane is fully configured to land, and the throttle pulled back, and the airplane slowing to a reasonable final approach airspeed. A separate pitot mast on the pilot's side of the fuselage senses local airflow (a combination of airspeed and propeller slipstream), and when the differential pressure across a flexible diaphragm falls below a certain amount, the gear extends using the normal electrically powered pump. Depending on your throttle setting and altitude, the airspeed at which the automatic extension occurs is from 78 to 103 knots indicated.

Of course, in an airplane used for high-performance training, such a system has benefits — and liabilities. For example, during stall and emergency training, there may be times when having the gear extend automatically makes the simulation unexpectedly exciting. So an override switch has been incorporated on Arrows as well. And with the ability to override the system comes, yes, the chance that a pilot will forget he or she has the override engaged. Yes, there's a yellow warning light located above the gear selector handle to remind the forgetful, but given that pilots have been known to ignore the big red "gear unsafe" light on the panel, there remains a chance that the pilot will miss that yellow light as well, and, in the face of all of Piper's good intentions, put the airplane in on its belly.

In fact, Piper issued a service bulletin (SB 866) recommending that the extension system be disabled. This followed a lawsuit against Piper brought by a pilot who suffered an engine failure in his Arrow and had the gear extend automatically — the resulting drag put him short of the runway. The moral of the story: A gear-up landing is generally preferable to one that takes place off the airport. The system also poses problems on short strips where quick retraction of the gear following takeoff is necessary for clearing obstacles. A further SB, 866A, allows owners to retain the system as long as certain conditions are met.

Another case in point: the "magic hands" system found on some early 1970s Beechcraft Bonanzas. An option offered by Beechcraft, the bellows-driven automatic extension system, proved relatively unpopular — and those that were installed seem to have been disabled in the intervening years. If you have a working system on your Bonanza, we'd love to hear about it.

Mistaken identity

The pilot of a Piper Twin Comanche reported that he had extended the gear as he neared the Auburn Municipal Airport in California, but the gear lights didn't come on until he was on downwind. In his statement to the NTSB, he noted that "after a normal touchdown, the airplane rolled down about one-third the runway length and the landing gear collapsed." However, a sergeant with the Auburn Police Department was making a routine check of the field at the time and saw the accident. In his report, he noted that the pilot confessed to him that "prior to touchdown, he had mistakenly moved the control lever for the wing flaps, rather than the control lever for the landing gear," which sadly resulted in the gear-up landing. In a particularly cruel twist of fate, a pilot can dutifully secure the gear down and locked in the pattern, only to mistakenly retract the gear prior to touchdown, or upon taxiing off the runway.

The urge to clean up the airplane generally doesn't strike until after the airplane has safely touched down; even then, it's best not to be too hasty about grabbing at flap switches lest you engage the gear switch by mistake.

Most modern retracts have systems designed to keep the gear from retracting on the ground. They accomplish this either through a switch on the gear itself (often referred to as a squat switch), activated by the pressure induced when the gear firmly supports the aircraft's weight, or through a switch tied to the airspeed indicator, which does not allow the gear cycle to begin if the airspeed is below a certain value — presumably one you'd reach after you'd lifted off. You need to understand how these systems work and how they might fail as well — both outright mechanical failure of the system and if it fails in its mission because of compounded pilot error.

One gotcha can occur if the gear lever is brought up by accident on clearing the runway — and not caught before the next takeoff. Once the airplane starts flying — and most of its weight is off the gear — the squat switch disengages and the gear cycle begins. The chances that the airplane settles back onto the runway at this time? High, of course.

What to do?

The best insurance against distraction, faulty systems, mindsets, and plain-old humanity is to come up with a series of habits and check phrases that are so ingrained in your cockpit technique that you've been known to recite them aloud in your sleep.

Some pilots get their first exposure to gear management while still riding on training wheels. That old approach mnemonic standby, "GUMP," in all of its permutations, begins with a G for gas and a U for undercarriage — interesting, since these are two things pilots are highly likely to mess up. First, before entering the traffic pattern, and after running a descent checklist if you are so bold, back yourself up with a trip through GUMP, and if your wheels are welded to the frame, so be it. There's no guarantee they are still hanging out there unless you look at them (if it's possible to do so).

Second, after you extend the gear, note how the airplane feels and flies differently than it does clean. The nagging sense that something doesn't feel right should always be your cue to go around, gain altitude, and assess that uneasy feeling. Since gear retraction is a critical part of most go-around procedures, your failure to drop the gear should be immediately obvious. Avoid at all costs the notion that you need to get on the ground now — unless you're on fire, this is rarely the case.

Third, you can incorporate some kind of final check. Back in my early days of complex-aircraft flying, I was taught that, on base, I should make a special call, out loud: "Capt. Stan says, 'Final clear, check the gear.'" This simple but illuminating phrase would cover two important areas: Is the final approach corridor clear of traffic before I turn onto it? And, of course, is the gear down and locked? I would vote for a phrase that suits you best, but the point is to make that phrase a no-brainer, every-time-you-land kind of thing.

I have no idea who Capt. Stan is, but I thank him for more than 3,000 gear-down landings so far.


E-mail the author at julie.boatman@aopa.org.


Good Gear Habits

By introducing several gear checks into your standard operating procedures — whether at a given moment you're using a printed checklist or a mental one — you'll cover contingencies and avoid letting distractions get to you. Here's where and when to check to take care of trouble spots:

  • Be aware when approaching the airport. Whether you use the gear to descend or not, pick a point outside the traffic pattern to put the wheels down as part of your before-landing checklist.
  • When in doubt, get the paper (checklist) out. We have Blackberrys and Palms and Filofaxes and Post-it notes for our ground-based lives; we owe ourselves at least that for our precious cockpit time, not to mention our airframes. Use the reminders that the manufacturer has provided for you, printed neatly on the checklist.
  • Engage the safety pilot. Though having two pilots on board isn't a panacea for gear-up landings, it can be if you share the workload. This reduces the effect of distraction and gives an opportunity for one pilot to catch the other pilot's error.
  • Check your downwind speed. If you're humming along on downwind, don't assume it's because the wind is 40 knots down the runway. That won't affect your indicated airspeed anyway. Yes, a properly configured airplane behaves differently, and you know when it feels right after some time in the make and model.
  • Final clear, check the gear. Use your base leg to look for traffic on final — and to make a positive check of the gear indicator lights and the gear's physical position.
  • Time on final? Check again. Be paranoid. It won't hurt.
  • Go around. But not if you've already heard scraping or grinding noises as the prop hit asphalt. If you haven't touched down yet, and something doesn't feel right, exercise your option to try again.
  • Leave it alone. Don't clean up the airplane until you are clear of the runway and have time to contemplate the switch you are about to move.

How do you remember to put the gear down? Share your tips with us at pilot@aopa.org. — JKB


An Extra Hand

Auxiliary gear advisory systems are available to provide one more warning in the event you configure to land without configuring the gear. AOPA has installed the P2 Audio Advisory System on previous sweepstakes aircraft (see " AOPA's 2001 Bonanza Sweepstakes: A Glass-Cockpit Bonanza," July 2001 Pilot) and will install a system on the 2005 sweepstakes aircraft, a Rockwell Commander 112A (see " AOPA Sweepstakes: Hurry Up and Wait," March Pilot).

The P2 system triggers when it senses that the airspeed has fallen below a preset value. Instead of merely sounding a horn, the system announces whether the "gear is down for landing" or whether the pilot needs to "check gear." The airspeed is adjustable based on the aircraft make and model, and can be selected in 5-knot increments. The system also annunciates overspeed conditions, based on V NE, and a stall warning, as well as providing a flight timer.
Price: $1,295
Contact: 888/921-8359; www.p2inc.com

Other landing-gear warning systems are available that use alternate means to trigger a warning. Airworld UK offers its Gear Alert system, which uses a transducer mounted on the belly of the airplane to sense when the airplane comes within 150 to 200 feet of the ground. At this point, a voice message, "check landing gear, check landing gear," sounds in the cockpit speaker or pilot headset. The voice system also may be set so that it is activated by the standard gear-warning horn on the airplane. Gear Alert is an FAA PMA (parts manufacturer approval) part.
Contact: www.airworlduk.com/gearalert.html

The Proscan FMS2000 is an aftermarket annunciation system that consolidates a number of warning and advisory annunciation lights in one place, especially handy in older cockpits where lights are scattered throughout the panel. The FMS2000 includes a red gear-warning light on its display to reinforce the gear location. The system also annunciates whether the gear-up and gear-down cycles are complete, prompts you to "check gear down" when airspeed falls below a certain value, and reminds you to bring up the gear after you accelerate above approach speed after takeoff. The Proscan FMS2000 is available through Eastern Avionics International.
Contact: www.avionix.comJKB