B737-800
Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Engineer; Flight Crew Multiengine; Flight Crew Instrument; Maintenance Powerplant; Maintenance Airframe
Flight Crew Last 90 Days 0; Flight Crew Total 15000; Flight Crew Type 2050
Situational Awareness; Training / Qualification; Communication Breakdown
Aircraft Equipment Problem Critical; Ground Event / Encounter Loss Of Aircraft Control; Ground Excursion Runway
General None Reported / Taken
Weather; Aircraft; Company Policy; Human Factors; Manuals
This is a continuation of two other reports. I demonstrated in those reports how the B737 aircraft landing gear geometry; through a lateral landing gear truck; hysteresis caused by heavy anti-skid cycling by individual wheels; causes a somewhat predictable hydroplaning phenomenon. This phenomenon although does not occur on every landing; but does occur at the most inopportune times; as demonstrated by numerous B737 runway excursions. In the last two years; there have been dozens of B737 runway excursions around the world. These excursions of course; always have some sort of extenuating circumstance; as explained in many of the accident reports. There is though almost always one common thread.  The statement by the pilots that the 'brakes were not effective.' The technique that we are taught in the B737 says for us to 'trust' the Anti-Skid System and let it do its work; even with the onset or either perceived or obvious hydroplaning conditions. This; I have demonstrated; is quite the opposite that one should do in certain situations. I made some recommendations in my report for possible techniques to be considered by pilots as well as additional contaminated runway testing; especially on non-grooved surfaces. I would like to emphasize that; I have personally experienced and demonstrated photographically in my report; how; with heavy braking on non-grooved runways; reverted rubber hydroplaning is guaranteed and actually predictable. Thereby causing potential nil braking conditions; down to taxi speeds; when pilots need the stopping ability the most. That is; when the aerodynamic braking abilities through [Engine] Reversers and air drag forces are insignificant at slower indicated airspeeds. I can argue professionally; demonstrably and statistically how; in every runway excursion; with or without either pilot or weather induced variables; my demonstrated hydroplaning findings are at least a contributing factor and many times a causal factor in all B737 runway excursions. The incident in ZZZZ is especially intriguing with evidence to support reverted rubber hydroplaning at slow speeds. First; I recall reading a report that indicated an Investigator saying '...runway looked as if it were steam cleaned by the Main Landing Gear (MLG) tires.' [Pictures I have seen] of the over run surface is clearly perturbed; as can be explained by the above 'steam cleaning' comment caused by Air Carrier X B737-800 Main Gear. The yellow chevrons in the over run are indications of this 'cleaning' effect. The white runway outline stripe has this cleaning effect as well and is easily seen. The most pronounced examples on the runway outline strip are the marks made by the Number 1 and Number 2 tires. The least noticeable; difficult; yet visible indication of reverted rubber hydroplaning 'steam cleaning;' is the 'cleaning' of the fifth from the left runway end makings.  The explanation that the pilots landed too long; too fast on a wet runway; is the obvious causal factor in this accident. Please do not let that distract from my point.  What I point out here is the almost guaranteed fact this aircraft as well as numerous other B737 incident/accident aircraft; have experienced reverted rubber hydroplaning caused by the lateral play in; and; geometry of the B737 gear truck as explained in my reports. I would like to point out that if Air Carrier Xs aircraft had been experiencing the 'typical' viscous or dynamic hydroplaning that is typical of most accident investigation findings; then the runway and over run surfaces would have not been as perturbed as they have obviously been. I would also like to emphasize the very real and significant potential to lose lateral control in even the most mild crosswinds; with potential 'nil' braking as demonstrated above. This easily explains the numerous lateral runway excursions.Be advised that I am currently working in a foreign country; at a very conservative; Part 121 style Air Carrier; flying the B737-800. My company has recognized these problems and has set very conservative crosswind and landing distance limitations; especially on non-grooved runways. Some Air Carriers know there is a problem and have taken action to prevent accidents. In fact; my current employer has a limitation of only a 25 knots permitted crosswind on a 'wet' non-grooved runway even though the braking action is 'good.' Bear in mind that Boeing has a demonstrated crosswind of 33 knots for winglet installed aircraft. In conclusion; there continue to be excessive B737 runway departures around the world that are easily explained by my findings; and potentially preventable with at least additional aircrew training and awareness. Additional testing and crew awareness is the minimal acceptable conclusion to my findings and concerns in my opinion. I ask that action be taken for passenger safety on the B737.I have been very outspoken as to my grave concerns about the B737 landing gear geometry contributing to excessive hydroplaning; especially at low speeds. This issue continues to confound both crews and accident investigators. I need to point out that the A320 for example; with very similar weights and tire footprints; has not demonstrated this phenomenon as indicated by the lack of crew complaints and similar type runway excursions; especially in the slow speed regime. That slow speed regime is on the order of 80 knots or less; but is not limited to this speed regime. A perfect example; one of the many dozens; of this phenomenon that led to an incident; was at ZZZZ in a foreign country. This is what started out as a typical; wet runway landing; and ended with a runway end excursion.The crew indicated that at about 60 knots; maximum braking was accomplished and the aircraft acted like it was on ice. This phenomenon has been experienced by me numerous times in a B737-800 and has led to numerous runway excursions both laterally and at the end; as in this case at ZZZZ. This crew at ZZZZ flew within acceptable landing parameters; had approximately 1;500 feet of runway left; at 60 knots; and still departed the end of the runway. This crew's 'ice' comments are an all too common comment and continue regularly to surprise crews. The typical explanations of rubber deposits; non grooving; oily surfaces; long landing touchdown; etc.; is disingenuous at best as other aircraft types are not demonstrating the same propensity to 'skid' as the heavier models of the B737 especially at slower speeds. I have yet to formally hear about my concerns a full year and a half after my first complaints. I have given all of my finding to my former employer who states my concerns are 'not safety of flight related;' with no further explanation given. I have written Boeing with no response. I believe it is the time to act before another serious runway excursion leads to injuries or deaths.Lastly; I would like to point out there is no evidence; yet; of a B737 near V-1; high speed; balanced field (stopping based balanced field); wet runway RTO. I am 100% convinced that if or when that happens; there will be a significant runway end excursion event; as the wet runway assumptions used by Boeing in this regime; do not apply based on my findings.
A B737-800 Captain revisits his concerns; using comparative analysis; that numerous B737-800 incident/accident aircraft have experienced reverted rubber hydroplaning on landing. A phenomenon caused by heavy anti-skid cycling by individual wheels and the lateral play in and geometry of; the B737 Main Landing Gear (MLG) truck assembly.