If the Before Landing checklist of the airplane you fly contains the phrase Gear down and locked, then its likely more than half of the reported accidents in your type of airplane involve operation of the landing gear. Landing gear-related mishaps – or any accident where the landing gear was a significant factor – consistently account for over half of all accidents in piston retracts.
Although they rarely hurt anyone seriously and often result in only minor damage, LGRMs are expensive. Some sources claim an average $40,000 to repair the results of a single-engine airplane involved in a mishap that results in only minor damage. LGRMs cost time, as it can take weeks or even months to repair the airplane.
Furthermore, a gear-related mishap in todays insurance environment can render the pilot virtually uninsurable for up to five years. Avoid LGRMs and youll avoid the hazard, the down-time, and the expense of landing gear accidents. And even pilots of fixed-gear airplanes feel the heat, paying higher insurance premiums as underwriters scramble to make back their losses from expensive landing gear-related claims.
Landing gear accidents come in several flavors. There are the characteristic gear-up landings in which the landing gear was not extended prior to landing with no apparent mechanical cause. These accidents are dominated by the pilot saying oops. Accidents can also be classified as gear collapses, in which the gear is extended but does not remain extended on the ground because of side loads or other reasons not related to mechanical failure. Finally, there are accidents in which there is a mechanical cause for the gear not to work normally. These include failures of downlocks and other parts of the gear extension system.
We did not consider instances where the landing gear failed because of a hard landing, collision with some object that damaged the gear, or a departure from the prepared surface of a runway.
Its Worse Than You Think
We conducted our study from preliminary FAA reports rather than preliminary NTSB reports, which explains why these numbers are much higher than the landing gear-related mishap statistics you may already be aware of. The statistics youve seen elsewhere tend to rely on final NTSB reports, but those tend to understate landing gear failures.
NTSB accident reporting criteria are contained in a document titled NTSB 830, Notification and Reporting of Aircraft Accidents or Incidents. The document states in section 830.5(a) that an aircraft operator is required to report an aircraft accident or incident. By NTSB definition, an accident is an occurrence … in which any person suffers death or serious injury, or in which the aircraft receives substantial damage.
The NTSB further defines substantial damage as damage or failure which adversely affects the structural strength, performance or flight characteristics of the aircraft. But, damage limited to … bent fairings or cowling, dented skin, small punctured holes in the skin … , ground damage to … propeller blades, and damage to landing gear, wheels, tires, flaps, engine accessories, brakes or wingtips are not considered substantial damage.
By definition, then, most landing gear related mishaps are specifically excluded from the reporting requirements of NTSB 830 and therefore are not included in most aviation safety studies. The NTSB decided long ago that they simply dont have the resources to investigate minor landing gear mishaps.
Theres no specific requirement to report to the FAA accidents that are not reportable under the NTSB definitions. The gear accidents that end up on the FAA web site do so because someone saw the results of a LGRM and assumed it needed to be reported to the FAA.
Once FAA hears of a mishap its obligated to investigate and issue a preliminary report, but thats as far as most LGRM investigations go. Therefore, the FAA reports present a more complete picture of the true frequency of aircraft mishaps, and in those reports gear-related mishaps account for over half of all incidents involving retractable-gear airplanes.
What Happened?
Based on the 403 FAA preliminary reports involving retracts issued during the first six months of 2002, nearly 52 percent were landing gear-related. Of those, 78 were gear-up landings, 103 were gear collapses and 28 had some immediately identifiable mechanical cause.
By far most of the gear up and gear collapse accidents were simply procedural errors on the part of the pilot. Often, though, the classic gear-up isnt an isolated event, but instead the end of a long chain of events created or obscured by some sort of distraction in the cockpit.
In many cases the pilot was performing touch-and-go practice and simply forgot the landing gear on what turned out to be the last circuit of the day. In fact, a fairly large number of the LGRMs happened with a flight instructor on board – and two sets of eyes, two pair of hands, and two brains failed to properly manipulate the landing gear.
Gear-up accidents often result from the distraction of open doors or windows in flight, or in the misleading visual cues accompanying low ground speeds and steep descent angles landing with strong winds near the surface. Occasionally youll see a preliminary report where the airplane experienced a total electrical failure and the pilot either forgot or simply did not know that there was a manual landing gear extension procedure.
Gear-collapse mishaps seem to often coincide with a desire to quickly reconfigure the airplane during the landing roll, either for a shorter landing or in the rush to progress from landing to takeoff in a touch-and-go. Many people are taught to retract flaps during the landing roll to increase braking effectiveness, but accidentally pull up the landing gear instead.
LGRMs identified with a mechanical cause are far less common than other LGRMs, but still statistically significant. In most incidents identified as such in the preliminary report the landing gear at least partially extends – sometimes one or more leg remains up. Other times, one or more strut doesnt fully extend. In these cases no manner of manual assistance or good wishes can get the gear the rest of the way down, and it collapses on touchdown.
Backward Gear Switches
Much is made of the supposed high incidence of LGRM in Beech airplanes, most of which have what is now considered a backward gear switch arrangement – with the little wheel on the right-hand side of the panel and the flap lever on the left. There are indeed a lot of gear-up and gear-collapse accidents in the Bonanza/Debonair and the Baron/Travel Air series, but theyre overshadowed by some other models.
The Cessna 210, for instance, seems to have a gear-up and a gear-collapse rate as great or greater than the Bonanzas because there are more mishaps but fewer 210s flying. Similarly, the Mooney singles – many with a big gear handle way up high on the panel precisely to avoid this problem – suffer high rates, as do the Cessna 310/320, the Piper PA-34 Seneca, and the Piper PA-24 Comanche.
Given this admittedly narrow study period, gear handle placement doesnt seem to be nearly as great a factor as some would believe.
Pilots, too, put great store in devices designed to protect them from landing gear-related mishaps. Most retracts have some sort of landing gear warning horn that activates when the power is pulled to near idle if the landing gear is not down. Unfortunately, these horns often sound a lot like a stall warning horn, and pilots improperly respond by adding a little power until touchdown, making the warning go away.
Many newer airplanes incorporate a link that triggers the gear horn if flaps are fully extended without a gear down indication. But from reports it seems they are not entirely effective either.
Perhaps the practice pilots do that puts them in situations where warning horns blare actually conditions them to ignore the warning horns when they need them the most. In fact, many gear-up pilots have reported they couldnt figure out what was wrong before touchdown because the horn was disrupting their concentration.
To prevent the gear-collapse mishap brought on by inadvertent pilot activation of the gear switch on the ground, most retracts have some sort of squat switch that interrupts power to the gear retraction mechanism when theres weight on the wheels. Dont depend too much on squat switches. The FAA web site is replete with accounts of inadvertent gear retractions during the landing (and sometimes even the takeoff) roll.
The reason the squat switch doesnt prevent them is apparent if you look at the mechanism. Many are small and easily contaminated with dirt. But even if its in good working order, it still may not protect you during taxi or a runway roll.
Many squat switches require only a very small movement of the landing gear shock strut to deactivate. You can defeat the squat switch simply by taxiing over a rough spot on the pavement or an expansion joint between two slabs of concrete. With a powerful gear motor, even this brief flexing of the strut can be enough to take the gear off the downlocks just as the airplane passes the dip in pavement and weight returns to the wheels.
I was able to test this theory in a Beech Baron that is equipped with dual squat switches, one on each main gear strut, and a BFGoodrich Skywatch traffic avoidance system. To prevent endless calls of traffic, traffic when taxiing around the airport, the Skywatch is wired into the gear squat switches and goes into standby mode when the Baron is on the ground.
I asked a passenger to watch the Skywatch system and simply say now at the point during the takeoff when the Skywatch switched from standby to active, scanning mode. I also asked he say now on landing at the point the Skywatch returned to the standby ground mode.
Id confirmed with BF Goodrich that there is no delay built into this squat-switch feature, so I determined that my experiment would tell me exactly when in the takeoff and landing procedures the squat switch engaged.
The squat switch seemed to work continuously in the takeoff until after rotation, except on rough runways or when hitting a semi-recessed runway light with a main tire. On landing, though, the squat switch remained open through the entire ground roll, not engaging until the airplane is almost completely stopped – at the FAA-recommended walking pace for taxi.
In this airplane, the squat switch will not protect you from gear switch activation during the landing roll or during a touch-and-go. It may not prevent gear retraction at the latter, high-speed end of a takeoff, or the beginning of a takeoff abort, depending on the runway.
The Stats
For many kinds of airplanes, the study period yielded too few mishaps to make the percentages meaningful. It only takes one incident, LGRM or not, to make a big difference in the percentage one way or the other. The more popular airplane types, which have a large number in the fleet and consequently a greater number of mishap reports, give you a more accurate picture of the LGRM epidemic.
You can also begin to infer that airplane design or panel layout has little to do with the number or type of LGRM.
The overall picture looks bleak because there are enough reports to get a good feel for the percentage resulting from landing gear mismanagement or maintenance problems. In fact, during no week during the first half of this year was the total number of LGRMs less than 50 percent of all FAA preliminary reports.
And remember that even the FAA preliminary reports dont provide the complete picture because many gear-related accidents are not reported to either the FAA or NTSB. Probably the best information would come from aircraft insurance companies, which probably hear about all LGRMs. Unfortunately for our study purposes, insurance carriers consider their loss data proprietary.
The gear-related mishap epidemic eats away at the active airplane fleet, costs innumerable dollars in repair costs and airplane downtime, may render the offending pilot uninsurable for years, and affects the cost of airplane insurance even for pilots of fixed-gear airplanes. Sometimes it even hurts someone.
No one wants to land an airplane gear up, or accidentally retract the gear on the ground. Actively work to avoid having a LGRM.
Also With This Article
Click here to view “10 Models with Most Frequent Mishaps.”
Click here to view “Tips for Avoiding Gear-Related Mishaps.”
-by Thomas P. Turner
Thomas P. Turner is an ATP who has written four books, including Cockpit Resource Management: A Private Pilots Guide. He has logged 2,000 hours of dual instruction given.
