The opinion of the court was delivered by: FOGEL
I. STATEMENT OF PROCEDURAL HISTORY AND FACTS OF THE CASE
On October 13, 1973, Cyrus H. Warshaw boarded Trans World Airlines (TWA) Flight 756 in Philadelphia which was bound for London. At the time he had an upper respiratory tract infection, but was otherwise in good health. The level of hearing in his left ear, on which a stapes replacement operation had been performed approximately thirteen years earlier, was essentially normal. Plaintiff claims he experienced a blockage in his left ear, which he was unable to clear during the aircraft's descent as it approached its destination at Heathrow Airport, near London. When he arrived at the terminal, he had completely lost hearing in that ear. Subsequent medical treatment, including surgery, did not cure the condition, one that has been diagnosed as permanent damage to the nerve of the left inner ear. Plaintiff and his wife accordingly instituted suit against TWA for damages as a result of this loss of hearing under the provisions of the Warsaw Convention, 49 Stat. 3000, as modified by the Montreal Agreement, 31 Fed. Reg. 7302 (1966). We tried the case without a jury on the sole issue of liability. We reserved decision with respect to that aspect of the case, pending receipt of further briefs from counsel for the parties who were directed to focus upon the single issue of whether or not this occurrence was an " accident " under the terms of the Warsaw Convention as modified by the Montreal Agreement. We hold that the occurrence was not an accident covered by the Convention. It appears that the question before us is one of first impression, which, to our knowledge, has not been decided squarely by any court on the facts before us. Our findings of fact, discussion, and conclusions of law follow:
1. Plaintiffs are Cyrus H. Warshaw and his wife, Sheila. Both are citizens and residents of the Commonwealth of Pennsylvania. (N.T. 24).
2. Defendant is Trans World Airlines, Inc. (TWA), a foreign corporation regularly doing business in Pennsylvania, with its principal place of business in Kansas City, Missouri. (Complaint, para. 2; Answer, para. 1).
3. Plaintiff Cyrus Warshaw travelled on TWA Flight 756 from Philadelphia International Airport to Heathrow Airport (metropolitan London area); he departed from Philadelphia on the evening of October 13, 1973, and arrived at Heathrow on the morning of October 14, 1973 (local time). Carriage had been contracted for in Pennsylvania, and Mr. Warshaw had been issued and had received the proper form of ticket for such an international flight. (N.T. 26; Complaint, paras. 4-5; Answer, para. 1).
4. Mr. Warshaw was suffering from the effects of an upper respiratory tract infection.
One of the symptoms of the plaintiff's illness was an aggravation during this flight of the mucus lining of the eustachian tubes; these small passageways run from the throat to the middle ear, and ordinarily, either by swallowing or yawning, one is able to equalize the pressure between the middle and outer ear. Because of his illness, Mr. Warshaw's eustachian tubes were blocked both by mucus and by the swollen linings of the tubes; thus, the tubes did not permit the passage of air necessary to equalize the pressure. (N.T. 32, 43-44, 55-57).
5. A normal human ear can be described as a mechanism which contains three interrelated systems: (a) the outer ear; (b) the middle ear; and (c) the inner ear.
(i) The outer ear includes the auricle (the flaps of skin which we commonly think of as the "ear"), and the ear canal, a passage running into the skull. The ear canal terminates at the ear drum, a piece of skin which vibrates as sound waves, (i.e., pressure variations in the atmosphere) strike it. These vibrations can best be characterized as " in-and-out ", the ear drum alternately pushing in and bulging out very slightly. (N.T. 47-57).
(ii) The middle ear consists of a chamber in the skull, separated from the outer ear by the ear drum and from the inner ear by two openings called the "oval window" and the "round window". A complex of three tiny bones, the malleus, the incus and the stapes (hammer, anvil, and stirrup), bridge the space between the ear drum and the oval window. Vibrations of the ear drum are multiplied some thirty times in force by the geometry of these tiny bones. The stapes "footplate", a small shaving of bone, sits in the oval window and vibrates in response to the vibrations passed through the three bones from the ear drum to the footplate. The round window is sealed by an elastic membrane that closes off the end of the inner ear (cochlea), which is not sealed by the oval window. The middle ear is connected to the pharynx (throat), by the eustachian tube, which permits the pressure inside the ear drum to be equalized to correspond to gross changes in pressure on the outer side of the drum.
Ordinarily, swallowing is done four times a minute, at which intervals the eustachian tube permits air to enter into or exit from the middle ear, thus equalizing the pressure. Were this not to occur, the ear drum would be pushed either to one side or the other of its normal, centered position, causing pain, possible injury, and perhaps a change in the hearing level. (N.T. 47-57).
(iii) The inner ear contains the cochlea, a fluid-filled labyrinth shaped somewhat like a snail shell, and the endings for the auditory nerves. Movement of the stapes footplate in the oval window sets up pressure waves in the fluid of the inner ear. The pressure waves excite the nerve endings, and stimulate electrical currents which the brain recognizes as "sound". (N.T. 49).
7. A stapedectomy is surgery performed on persons who suffer air conduction hearing loss due to otosclerosis, but have not suffered severe bone conduction loss of hearing. The procedure is as follows: the middle ear is penetrated through an opening which has been made in the ear drum. The calcified stapes footplate and oval window are fractured, the pieces are removed, and a replacement is fashioned out of plastic, steel, fat, tissue, or other materials. Such an operation was performed on Mr. Warshaw's left ear in March, 1961; a piece of plastic tubing was used to replace the stapes, and a vein graft performed to close the oval window. The plastic tubing was fitted into the center of the vein graft; it transmits vibrations to the fluid in the inner ear. The vein graft, a flap of tissue taken from another vein in the body, closes off the opening to the inner ear and to the fluid chamber, while permitting vibrations to pass. The operation has a high probability of success when performed on patients who are amenable to such treatment; it was extremely successful in Mr. Warshaw's case. Indeed, he and his doctor decided that it was unnecessary to proceed with a similar operation on the right ear. (N.T. 29, 51-52, 58).
8. At the time of the flight in 1973, Mr. Warshaw's hearing in his left ear was normal, as demonstrated by auditory tests, personal experience, and observation by two business associates who were on the same flight and who had the opportunity to observe Mr. Warshaw both during the prior twelve month period, as well as the fifteen to thirty minute interval immediately prior to embarkation. (N.T. 6-10, 15-23, 29).
9. An individual who has undergone a stapedectomy is no more sensitive to air pressure changes than ordinary persons, if the eustachian tube is open and functioning. However, such a person may be more sensitive than others to such pressures if the tube is in fact blocked. (N.T. 100-04).
10. The aircraft was a Boeing 707-331C, serial number 20428, an aircraft used commonly for trans-oceanic flights. That aircraft had been issued a "Standard Airworthiness Certificate" on July 24, 1970. (Exhibit D-1). The parties have stipulated that it was operating in normal fashion at the time of the flight, and suffered no malfunctions during the entire flight.
11. The routine flight altitude for a Boeing 707 on a transatlantic flight is between 30,000 and 40,000 feet. (N.T. 61, 65, 86).
12. Because the air at such altitudes is too thin to support human life comfortably, if at all, such airplanes are provided with a cabin pressurization system. The system can operate either manually or automatically, depending in part upon how changes in cabin pressure are controlled, and in part upon the rate of change which is possible. The system on Flight 756 was operated automatically. Thus, there was a maximum pressure differential of eight and six-tenths pounds per square inch between sea level pressure and altitude. Moreover, the change in cabin pressure can be varied at a rate equivalent to the variation in the external atmospheric pressure surrounding the plane for rates of descent or ascent ranging from fifty to two-thousand feet per minute. Valves built into the automatic system close off the cabin vents when the pressure differential from sea level reaches the preset limit; i.e., eight and six-tenths pounds per square inch. Documents produced by defendant and introduced by plaintiff, relative to the operation of the aircraft's systems, establish that in the ordinary course of events the valves close off the cabin above an altitude of 13,000 feet. (Exhibit P-2; Answers to Interrogatories).
14. Pressure at sea level is approximately fourteen and seven-tenths pounds per square inch. Therefore, the internal cabin pressure at maximum altitude is approximately six pounds per square inch; when the landing is at a low altitude airport such as Heathrow, the pressure at that point is close to the fourteen and seven-tenths pound level, or more than twice the six pound pressure at maximum altitude. (Exhibit P-2, Answers to Interrogatories; N.T. 75-83).
15. There are no records available with respect to the rate of change of the cabin pressure during repressurization. (Answers to Interrogatories). However, Dr. Myers, the plaintiff's medical expert, testified that his determination of possible relationship to ear damage did not require him to have the rate of change of pressure, because of the following information he had: FIRST, data about the gross change in pressure; and SECOND, his factual assumption that the plaintiff's eustachian tubes were either completely or substantially blocked. (N.T. 68).
16. At some point during the descent and repressurization of the aircraft, plaintiff experienced blockage of his ears. He attempted to clear his ears by swallowing, but was unable to do so. He was not concerned at the time, because he anticipated that he would be able to clear his ears shortly after landing. However, he was unable to equalize the pressure during the entire period which is critical to this action. (N.T. 30-33).
17. Shortly after their arrival at Heathrow, Plaintiff's companions realized that Mr. Warshaw was unable to hear unless they shouted at him when they were virtually toe-to-toe with him. Mr. Warshaw found that he could not hear in his left ear, and had limited hearing only in his right ear. This represented a sharp change for the left ear, although probably no change at all for the right ear; that ear was also afflicted with otosclerosis, and had not been subjected to any curative operation. (N.T. 9, 20-22, 33).
18. Plaintiff's condition failed to improve despite treatment with antihistamines during the approximate five-day period he was in England and Ireland. (N.T. 34-38).
19. Upon his return to the United States, Plaintiff was examined by Dr. Myers and his associate, Dr. Schlosser, both of whom are ear, nose and throat specialists. (Dr. Myers testified that he was Board-certified in his specialty in 1935). (N.T. 38-39, 41; Exhibit P-1).
20. These examinations showed losses of both air conductive and bone conductive hearing. The air conduction loss was so substantial that the doctors believed the probable cause, given the past stapedectomy, was slippage of the plastic tube prosthesis from the end of the incus bone. However, an operation was necessary to confirm this, and to remedy the situation, if, in fact, that was the problem. (N.T. 43, 55-59).
21. The operation disclosed that the prosthesis was still properly attached to the incus. However, there had been considerable damage at the point at which contact was made with the vein graft that closes the oval window. The region was cleaned, and another prosthesis was fashioned to replace the damaged one, after which the ear was again closed. (N.T. 58-60; Answers to Interrogatories).
23. Dr. Myers was asked a hypothetical question which included the following facts as premises: (a) the pressure differential from altitude to sea level; (b) the fact that all systems on the plane functioned normally; (c) the inference that would flow from the fact of an individual undergoing a successful stapedectomy on the left ear of the type performed on plaintiff thirteen years earlier; (d) the fact that an individual had an upper respiratory tract infection at the time of the flight; (e) the fact that that individual had good hearing in his left ear prior to a transatlantic flight; (f) the fact that during the descent he felt a blockage in his ears which he was unable to clear; (g) the fact that upon reaching the airport terminal he found that he had lost all hearing in his left ear; (h) the fact that the hearing loss was a continuing one; and (i) the fact that the results of the medical testing, observation and surgery were the same as those which flowed from the actual tests, observation and surgery which Mr. Warshaw underwent.
He was asked if he could form an opinion with respect to the cause of deafness from this information. He stated that, in his opinion, the cause of deafness was a traumatic injury to the inner ear nerves, which was caused by the unequalized pressure change displacing the ear drum, attached bones and prosthesis so that the prosthesis penetrated into the inner ear. (N.T. 89-92).
24. We find, on the basis of the foregoing medical opinion from a duly qualified medical expert, and on the basis of all the evidence adduced for the purpose of justifying the assumptions of the hypothetical question, that the cabin repressurization as Flight 756 descended to London was a cause of the damage to plaintiff's left ear. We also find, on the basis of Dr. Myers' testimony and the relevant evidentiary facts, that the injury was in part caused by the peculiar condition of plaintiff, who had undergone a stapedectomy, and was suffering from a cold at the time. However, that was not the sole cause, because such an injury could have occurred even had he not suffered from a cold; such an impairment could have occurred to an individual with normally functioning middle ear bones.
25. We find credible, and therefore accept, plaintiff's testimony that he did not anticipate nor consider the possibility that he could be subject to such an injury if he took this flight while suffering from a cold. (N.T. 116-117). We also find credible, and also accept, plaintiff's explanation that he thought the blockage of his ears stemmed from the cold, until such time as he was examined by an ear specialist when he returned to the United States. Accordingly, he did not notify the defendant either on the plane, at the terminal at Heathrow, or, ...