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So, the Learjet 60 that I used to fly has the following limitation:

Learjet 60 AFM page

My question, is why would a manufacturer certify an airplane for ditching if it isn't required? The airplane is most likely going to be totaled anyway, right?

Or does it just mean that since it isn't certified for ditching that we aren't allowed to do it? Guess no double engine failures over water will be in my near future....

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  • $\begingroup$ This doesn't directly relate to the question, but the A-320 that Sully ditched in the Hudson River had a "ditching switch". Flipping this switch closes all through-hull fittings to make the plane less likely to flood and sink - of course structural damage or even open doors and windows can sink the plane quickly. But the ditching switch is intended to give the crew and passengers more time after splashdown. NB Sully and Skiles forgot about this switch and ditched successfully with the switch not activated, so it just helps in the landing but - as demonstrated - it is possible to survive the di $\endgroup$ – Skip Miller Jan 10 '14 at 16:59
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I think that 14 CFR 25.801 might sum this one up. Aircraft that are approved for ditching under 25.801 have to meet several requirements:

(b) Each practicable design measure, compatible with the general characteristics of the airplane, must be taken to minimize the probability that in an emergency landing on water, the behavior of the airplane would cause immediate injury to the occupants or would make it impossible for them to escape.

(c) The probable behavior of the airplane in a water landing must be investigated by model tests [emphasis mine] or by comparison with airplanes of similar configuration for which the ditching characteristics are known. Scoops, flaps, projections, and any other factor likely to affect the hydrodynamic characteristics of the airplane, must be considered.

(d) It must be shown that, under reasonably probable water conditions, the flotation time and trim of the airplane will allow the occupants to leave the airplane and enter the liferafts required by § 25.1415. [emphasis mine] If compliance with this provision is shown by buoyancy and trim computations, appropriate allowances must be made for probable structural damage and leakage. If the airplane has fuel tanks (with fuel jettisoning provisions) that can reasonably be expected to withstand a ditching without leakage, the jettisonable volume of fuel may be considered as buoyancy volume.

(e) Unless the effects of the collapse of external doors and windows are accounted for in the investigation of the probable behavior of the airplane in a water landing (as prescribed in paragraphs (c) and (d) of this section), the external doors and windows must be designed to withstand the probable maximum local pressures.

Basically, the aircraft needs to have its hydrodynamic behavior while ditching investigated, and it must then float long enough for the occupants to escape. It sounds like the Learjet 60, if ditched, is not guaranteed to either a) remain structurally sound, or b) allow the crew and passengers to get out before it slips below the waves.

An aircraft that was certified for ditching, on the other hand, basically means two things:

  1. The crew knows that they have at least a chance of doing it right (and will possibly change how the aircraft is configured or prepared), probably with an actual published checklist available to them; and:
  2. If the crew screws it up, it's their own fault and the manufacturer might not be held liable; the aircraft met certification standards. This would significantly reduce their liability in a crash. It's probably mostly that one, honestly.
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    $\begingroup$ Nice and correct answer. It's a legal thing and something the crew of cause should have in mind for decision making but if they are in an emergency and they still consider it to be the safest way to ditch, this limitation should not be the reason why they crash attempting to avoid the ditching. $\endgroup$ – Falk Jan 10 '14 at 4:13
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    $\begingroup$ The main gist of my question is why would one jet be certified for it and another not? If it isn't required, I'm honestly surprised that any of them do it based on how the aviation industry normally does these things. What benefit does the manufacturer gain by certifying an airplane for ditching? $\endgroup$ – Lnafziger Jan 10 '14 at 5:05
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    $\begingroup$ Airliners conducting extended overwater operations have to be certified for ditching. $\endgroup$ – xpda Jan 10 '14 at 7:29
  • $\begingroup$ @xpda It may have something to do with this. I doubt that too many people will be doing atlantic crossings in the Lear! $\endgroup$ – Lnafziger Jan 10 '14 at 15:12
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    $\begingroup$ @Chad there are various requirements to be met that determine how far from land you can be. The EMB-145 I flew could only do 50 nm offshore (no life rafts among other things), but we still serviced the Bahamas. You just had to plan a route that kept you legal. Same way we serviced the Yucatan in Mexico, by taking the long way around the Gulf of Mexico to get there. $\endgroup$ – casey Jan 10 '14 at 21:46

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