By Thomas P. Turner
More than eight times each week. Well over $1 million every month. These are very conservative estimates of the rate of gear-up and gear-collapse landings among factory-built, piston-engine airplanes in the U.S., and what the U.S. aviation insurance industry pays in gear-related claims.
Studying the problem of landing gear-related mishaps (LGRMs) for over six years, Ive been able to identify repeated patterns. By recognizing and learning from these patterns, we can develop techniques for avoiding LGRMs.
More Than You Think
The number of gear-related mishaps is much higher than most studies would lead us to believe. Most LGRMs are by definition exempt from NTSB reporting requirements. Unless a passenger is seriously injured, or damage goes beyond propellers, gear doors, cowlings, flaps and lower surfaces-the typical results of gear-up and gear collapse landings-NTSB 830 (the mishap reporting regulation) specifically says it does not want a report. Since virtually all mishap studies take their raw data from NTSB, the true number of gear-up landings is vastly underreported.
Many more LGRMs show up on FAA preliminary reports. The FAA tells us there is about one LGRM every day in the U.S. This figure, too, is likely low … there is no requirement to report LGRMs to the FAA unless an emergency was declared.
The high rate of gear-up landings costs us all. Insurance sources report the typical gear-related mishap claim costs between $40,000 and $60,000 to administer. Using the low-end figure and the (underreported) FAA numbers, the U.S. insurance industry pays well over $1 million every month in LGRM landing claims.
As weve said, the actual number is likely far higher. Imagine trying to justify that expense to insurance company shareholders. No wonder insuring a retract is more expensive than similar, fixed-gear models, or that the experience requirements to insure an RG airplane are much higher than comparable fixed-gear designs.
The cost of gear-up landings goes beyond just insurance. Although rarely is someone hurt in a gear-up landing, there are significant exceptions, so gear-ups present an injury hazard to pilots and passengers. Airplanes, propellers and engines are very expensive to repair, so increasingly the cost of repairing gear-up damage is great. Often an airplane is totaled after a seemingly benign gear-up landing-especially as the fleet ages and parts become expensive and scarce-meaning that more and more airplanes are withdrawn from service, raising industry economy-of-scale costs for the rest of us, retractable-gear or not.
What could be more fundamental than putting the wheels down before landing? So why are gear-up landings so common?
Gear-up landings result from two things: pilot distraction and deviation from a normal routine. Anything that interrupts the pilot at a critical time can contribute to a gear-up landing. Poor pilot procedure can prevent a pilot from catching the error before its too late.
One reason gear-up landings are so common, in my opinion, is that pilots do not take the time during a retractable-gear checkout to ingrain a new habit pattern for landing, one that is different from that used in fixed-gear airplanes. Say youre flying downwind in a fixed-gear airplane. When you want to begin your descent from pattern altitude, what do you do to initiate the descent? Reduce power and the airplane begins to descend. Do this a few dozen or hundred times and you dont even think about the need to reduce power to descend.
Now you move into a retractable-gear airplane. What might you do when its time to descend from pattern altitude? Extend the gear. In most retractable-gear airplanes, extending the landing gear causes the airplane to enter a roughly 500 foot per minute descent. Using the landing gear to initiate descent from pattern altitude achieves the performance requirement while helping you prevent a gear-up landing.
But say you get distracted by other traffic, or a sick passenger, or any number of other things just as youre ready to descend below pattern altitude. If you revert to whats most familiar to you, what you first learned in fixed-gear airplanes, youll pull power to begin your descent.Pull enough power and the airplane will go down. If you continue to be distracted and dont deliberately check gear position, the first indication that you forgot may be the chopping sound the propeller makes when it contacts the pavement.
The law of primacy tells us that when distracted or under stress we tend to do things the way we first learned them. Initial checkout in retractables needs to include sufficient practice to permanently replace these habits ingrained from flying with the gear welded down. Clearly, the mishap record shows the traditional three times around the patch RG checkout is not sufficient to avoid gear-up landings.
Proper RG landings must include a final-approach check of gear position. I like to do this verification no lower than 400 feet agl. This is in addition to the proverbial GUMP check (for Gas, Undercarriage, Mixture and Prop), which really should be done further from the airport, with Undercarriage delayed until leaving pattern altitude. A short-final check of gear position provides plenty of time for a smooth go-around if you find the gear is not down.
Ive found there are several common contributing factors in gear-up landings:
Modified pattern. Often a gear-up landing results when another airplane interrupts the pattern for the retractable-gear airplane. Airplanes cutting ahead in the pattern, taking off or landing in the opposite direction (or on an intersecting runway) may cause the RG pilot to have to modify his or her approach. This results in a non-standard pattern that interrupts the pilots habits, and may contribute to forgetting the landing gear.
Strong or gusty surface winds. Strong surface winds usually mean low-altitude turbulence, which itself can be distracting. Turbulence may lead to distraction from nervous or sick passengers. On the downwind leg in windy conditions, groundspeed is high, rushing the pilot and perhaps interrupting the flow of events. Turning onto final approach into strong winds, groundspeed will drop, and the angle of descent over the ground will steepen. Both result in visual cues that make it look like the airplane is descending with the landing gear down.
Electrical failures. Since most retractable gear is powered by electric motors or by hydraulic systems that are in turn electrically activated, an alternator or generator failure may contribute to a gear-up landing. Sometimes the pilot is so distracted by the electrical failure that he or she forgets to extend the landing gear.
Instructor on Board. From my research, the most common correlating factor in LGRMs is (of all things) flying with an instructor pilot on board providing dual instruction. The CFI-involved LGRM does not always occur during an initial checkout in the airplane-instead, it often happens with an experienced pilot receiving a flight review.
Youd think having an instructor pilot on board would make a gear-mishap landing almost impossible. As an instructor, however, Ill tell you it is easy to become complacent as the lesson progresses. And pilots often act differently when theres a CFI in the right seat. Often its the third or fourth time around the traffic pattern when the dual-instruction gear-up landing occurs.
Warning Systems. Most RG airplanes have gear-up warning systems, but there are normal flight situations where warning systems wont help. For instance, most gear warning horns are rigged to sound when the throttle is brought to idle if the gear is not down. But if you use power to touchdown, which many pilots do in windy conditions or to cushion even a normal landing, the gear warning horn may not sound.
In some airplanes the gear warning also sounds if the flaps are fully down when the gear is not. This warning only works, however, if you select full flaps; some pilots dont use full flaps for every landing (especially in high winds), and in these cases the warning will not work.
Some airplanes have a system where the gear warning also flashes an annunciator on the instrument panel. Pilots generally focus their attention outside the airplane on final approach, however, and may not see a cockpit warning. Conditions that prevent the gear warning horn from sounding will also inhibit the annunicator light.
If you make full-stall landings you get used to hearing the stall warning horn on touchdown. You may not notice the difference between a steady stall warning and the intermittent gear advisory.
Lastly, modern noise-canceling headsets often prevent the pilot from hearing a warning horn, unless the airplane has been modified to pipe the warning through the intercom.
Gear collapses, where the gear is down but does not stay down on the ground, are even more common than gear-up landings. Very typically the airplanes nose landing gear folds up near the end of the landing roll. Rarely, the gear collapse happens on takeoff, or even during taxi. What has happened?
Wrong handle. Of those gear-collapse mishaps where there is an identified cause, most result when the pilot inadvertently retracts the landing gear. How can this happen? Some airplanes operating manuals recommend retracting flaps after touchdown to put more weight on the wheels and enhance brake effectiveness. The record shows that many pilots achieve extremely shorted ground rolls by accidentally moving the gear handle instead of the flap control.
It seems best in retractable-gear airplanes to delay any reconfiguration of the airplane until clear of the runway and, preferably, at a complete stop that provides time to confirm handle selection before retraction.
Touch-and-goes. This is likely even more of a problem during touch-and-go landings, because a touch-and-go by nature requires a rapid reconfiguration during a short period while moving quickly down the runway.In my opinion its best to avoid touch-and-goes in all retractable gear aircraft. If you must perform them, do so only with an instructor pilot and then only after clearly briefing responsibilities beforehand. For instance, the pilot flying should accomplish all reconfiguration tasks except for resetting flap and trim for the go-items that move the pilots hand quickly to the vicinity of the landing gear handle. The pilot not flying (CFI) should reconfigure and retrim the airplane on the go. In all cases (again, in my opinion based on years of study), RG pilots should not conduct touch-and-go landings solo, without prebriefing another on-board pilot who can reach the controls, or with a nonpilot in the other seat.
Squat switches. Most retractable-gear airplanes have switches on at least one landing gear leg preventing power to the landing gear motor if the airplanes weight is resting on the wheels. Dont trust them. Failed switches or overly pumped-up landing gear struts can render the switches ineffective.Small up-and-down strut movements (such as from rolling over bumps or expansion joints on pavement, or depressions on a grass runway) may close the squat switches long enough for a gear motor to disable gear downlocks. It may take most of a landing ground roll for the airplane to settle fully onto its struts and activate the squat switches. Safeties notwithstanding, your only defense against inadvertent gear retraction on the ground is to avoid moving the landing gear handle to up.
In a small minority of reported cases there is an identified mechanical failure that leads to gear up or gear collapse mishaps. Most frequently its a failure of a gear pushrod or rod end, or landing gear systems that are so badly out of rig that they cannot support landing or takeoff forces.Occasionally with hydraulic systems theres a seal break or other hydraulic fluid loss that prevents gear extension or allows premature retraction. Sometimes items as simple as worn bushings or broken gear shims can cause failure.
Most retractable gear airplanes now flying have been in service for decades, likely far longer than their designers envisioned. Its possible to keep these airplanes in great mechanical shape, ensuring safe operation for years to come. But retractable landing gear is complex machinery, requiring progressively more work as the system logs more and more cycles. The constant effort (and cost) necessary to keep gear systems airworthy is becoming much greater than historically has been the case. I suspect that many gear collapse mishaps have an unreported maintenance and overhaul component.
Being One Who Wont
Anyone can forget to extend the landing gear on any given day. Total time and time-in-type alone do not protect us from natural human failings-we have to consciously work to avoid a LGRM every time we land the airplane.
Theres an old saying about flying airplanes with retractable landing gear: There are those that have, and those who will have a gear-related mishap. Concentrate on extending and verifying the landing gear every time you land, and youll not be one of those who have, or those who will-youll be one of Those Who Wont.
-Tom Turner is a CFII-MEI who frequently writes and lectures on aviation safety.