May 12, 2014
By Barry Schiff
Every once in a while, a hangar-flying session involves debating the best and worst types of aircraft to use when ditching (assuming that one had a choice at such a time). I recently overheard such a discussion at my local airport, and it reminded me of research I did about this subject more than 30 years ago. Most pilots, I discovered (then and now), believe that the ideal light airplane for ditching has low wings and retractable landing gear. Statistics, however, do not appear to substantiate this.
Although low-wing airplanes do offer superior planing and buoyancy (especially when fuel tanks are empty), they usually should not be landed in water with their wing flaps significantly extended because this can cause a pronounced nose-down pitching moment and make the aircraft behave like a submarine. Also, extended flaps on a low-wing airplane can be torn away during touchdown. This can create openings in the wing structure and have an undesirable effect on buoyancy. Without flaps, low-wing airplanes typically splash down at a greater speed, which increases the likelihood of injury.
Because the flaps of high-wing airplanes are less susceptible to water damage, they can and should be used to the maximum extent possible to reduce touchdown speed.
Another disadvantage of a low-wing configuration is that it is easier to inadvertently dig a wing tip into the water (especially when landing in a rolling sea), and this can result in cartwheeling. The ailerons on high-wing airplanes are more effective in maintaining lateral control because they can be kept high and dry during the initial phase of the landing.
Although a ditching should be made with the landing gear retracted (when possible), this should not be construed to mean that retractable-gear aircraft are more suitable than fixed-gear aircraft. Just the opposite might be true. Of the 104 ditchings made in U.S. waters during the three-year period under study, half were in retractables, yet these accounted for two-thirds of the fatalities that occurred during splashdown. These statistics likely are the result of retractables typically having higher stall and landing speeds, which obviously result in greater deceleration and impact forces.
When touching down on a clean belly, the aircraft tends to skip, just the way a flat, spinning rock does when tossed toward a deep puddle at an acute angle. The initial touchdown can be quite mild—but hang on. The second impact is likely to be much more severe, especially as the elevator loses effectiveness (because of airspeed decay) and the nose digs in. This can cause the aircraft to submerge quickly. It most often, however, bobs back to the surface and provides some time for evacuation (unless the front windshield has imploded and the aircraft floods).
Those who have ditched slow, fixed-gear aircraft most often report that the main gear digging in during initial touchdown prevents aircraft skipping and the subsequent striking of the water in a nose-low attitude. Instead, the aircraft simply decelerates rapidly with the nose burrowing only slightly. It is generally agreed that this is safer than having to endure the secondary, nose-low impact associated with ditching retractables.
Although initial touchdown should be made as slowly as possible, a full-stall landing should be avoided because of the possibility of the nose dropping and causing the airplane to strike the water nose first. Instead, it is recommended that fixed-gear airplanes land in a 10- to 12-degree nose-high attitude and retractables in a five- to eight-degree attitude.
Most airplanes come to a stop in a nose-down attitude because the center of gravity is typically ahead of the center of buoyancy.
Considering the variables, there does not seem to be a consensus as to the optimum aircraft for ditching— except that perhaps it should have STOL characteristics, be built of wood, and be stuffed with ping-pong balls. This study, however, was made prior to the advent of aircraft equipped with full-airframe parachutes. Given the choice, I think I would be tempted to select a Cirrus. I presume that it would simply plop onto the water with hardly any horizontal forces to threaten those inside.
The U.S. Coast Guard says that approximately one-fourth of all ditchings involve fatalities and points out that most of those who perish survived the ditching itself. Most fatalities occur after evacuation and usually are caused by drowning because flotation devices are unavailable, out of reach, are damaged during evacuation, or fail to inflate.
Ever wonder why landing a landplane in water is called ditching? It originated as a Royal Air Force term that meant landing in the English Channel, which was colloquially known as “the ditch.”
Barry Schiff has been writing for AOPA Pilot for 51 years. This month marks the anniversary.
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