What happens when you mix ageing eyes with ageing aircraft?
Getting older often means some things getting soft (like our bellies) and other things getting hard (like the lenses in our eyes). Diet and exercise can help with the belly, but there’s not much you can do if cataracts begin to develop — no drops, glasses or exercise can stop the progression. Of course, if things get too bad, surgery can replace our worn-out natural lenses with artificial optics. The surgery is really quite safe and effective.
I’m writing about cataracts this month because the NTSB has reached out to the pilot community urging us to be aware of the dangers slowly progressing cataracts can present for some piloting activities — especially night operations. And I suspect that the NTSB knows that a pilot can demonstrate vision corrected to 20/20 during his FAA medical exam and yet still have troublesome cataracts. Of course, we are all proud to demonstrate our 20/20 corrected vision to the aviation medical examiner (AME) but probably a bit reluctant to confess that we’re beginning to suffer from headlight flair when driving at night, or that the stars in the night sky seem to be ringed with halos.
The NTSB’s interest in cataracts arises from its investigation into the Dec. 26, 2013, loss of a Cessna 172 during a night VFR approach at Fresno, California. The 72-year-old pilot and his passenger were killed and the aircraft destroyed in the crash after the pilot made several unsuccessful passes at the runway.
Specifically, the Safety Board has asked the FAA “to develop educational information for pilots [based on this accident] and the risks cataracts may pose to flight safety including a discussion of degraded vision at night, and encourage pilots with cataracts to communicate with their eye care professionals regarding diagnosis and treatment options.”
The Safety Board adds that there is “limited educational information provided to pilots and aviation medical examiners concerning the hazards cataracts pose to flight safety, especially at night.”
The Accident
The Cessna 172K, N251JM, struck the ground about 1820 PST while maneuvering near Fresno Chandler Executive Airport (FCH). The airplane was being operated under FAR Part 91. Dark night VMC prevailed for the cross-country flight that originated at 1643 from the pilot’s home base at Tehachapi, California, some 125 mi. to the southeast.
The Fresno Yosemite International Airport (FAT) AWOS, located 6 mi. northeast of the accident site, recorded conditions at 1953 as: wind from 320 deg. at 3 kt.; visibility, 5 mi.; haze; clear sky; temperature, 10C; dew point, 3C; and an altimeter setting of 30.24.
Fresno Chandler Executive Airport — elevation, 279 ft. — is a non-towered facility with a single 3,627-ft.-long, 75-ft.-wide, asphalt runway marked 12/30. On the night of the accident, Runway 30 was equipped with a four-light PAPI light system, oriented on a 3-deg. glideslope and a 438-ft. displaced threshold. The edges of the runway were marked by white runway lights. Two strobe lights marked either side of the runway at the threshold. Red lights marked the displaced threshold. Green lights marked the beginning of the usable runway. The runway lighting system was controlled by the CTAF frequency after airport operation hours.
The pilot had been receiving VFR flight-following services from ATC. When the flight was about 10 mi. south of the airport, the pilot notified ATC that he had the airport in sight. ATC canceled flight following and approved the pilot to change frequencies at 1802.
Several witnesses located adjacent to the accident site and airport told investigators they observed the accident airplane enter the airport traffic pattern for Runway 30.
One witness located on the ramp area stated that the airplane initially captured his attention when it landed hard about midway down the runway, then proceeded to take off again.
Witnesses watched as the airplane continued on a northwesterly heading and maneuver for landing on Runway 12, where they observed the airplane flying at a high rate of speed about 10 to 15 ft. AGL. The witnesses stated that the airplane entered a climb about three-quarters of the way down the runway and continued to the southwest where the pilot performed a series of turns.
Witnesses then watched as the airplane approached Runway 30 again. Two witnesses located midfield reported observing the airplane fly along the runway about 100 ft. AGL and noted that the left wing navigation light appeared to be inoperative. The witnesses told investigators that as the airplane neared the departure end of Runway 30 at an altitude of about 400 ft. AGL, it rolled to the left and descended in a vertical attitude below their line of sight behind a row of hangars.
Airport security cameras captured the lights of the accident airplane maneuvering over the runway. Runway lights were activated at 1811:54. The camera recordings ran from 1813:44 to 1819:50 when the lights of the airplane descended rapidly toward the ground. The photo sequences were consistent with the reports of the observers.
The Pilot
The pilot held a private certificate with an airplane single-engine land rating. A third-class airman medical certificate had been issued to the pilot on May 15, 2013, with the limitation that he “must possess glasses for near vision.” The pilot had accumulated about 1,500 total flight hours of which 25.3 hr. were at night. His most recent flight review was completed on Jan. 22, 2013.
A witness located at Tehachapi Airport — the pilot’s home base — told investigators that he observed an incident after sunset about three weeks before the accident. In that event, he watched the accident pilot about 20 ft. above the ground, landing on Runway 11. After the airplane landed, the witness noticed it taxiing in a direction away from its hangar. Using a handheld radio, the witness queried the pilot if he was going to his hangar, since his normal parking area was in the opposite direction. The pilot replied “. . . no, I am trying to find the taxiway.”
The witness stated that he asked the pilot what he meant by “. . . trying to find the taxiway,” and the pilot responded, “I can’t find the exit off the runway.” The witness instructed the pilot to remain in his current location. Then the witness used his vehicle’s headlights to illuminate the taxiway, and assisted the pilot to exit the runway. After that, the witness stated the pilot said thanks and continued to parking. He added that at the time, the runway and taxiway lights were illuminated.
The Investigation
The Safety Board investigator in charge, with the assistance of a Fresno Police Department Helicopter, flew a VFR approach to Runway 30, with the PAPI indicating two white and two red lights the day following the accident. Throughout the entire approach, the descent was normal and no irregularities were noted. The investigator reported that the helicopter’s altitude was about 100 ft. above the trees as it passed over the tree that the investigation revealed the accident airplane had struck.
Multiple paint chips, landing light cover lens fragments and a portion of the left fiberglass wingtip were found at this location, 1,406 ft. southeast of the approach end of Runway 30. The tree, about 62 ft. tall, exhibited numerous broken branches about 40 to 45 ft. above the ground.
Meanwhile, the primary accident site revealed that the airplane struck the ground about 490 ft. southwest of the departure end of Runway 30. All major structural items of the airplane were located within about 50 ft. of the main wreckage, except for a portion of the outboard left fiberglass wingtip.
The wrecked Cessna was heavily damaged by impact forces and fire, but flight control continuity was established throughout the airframe from all primary control surfaces to the cockpit controls. The elevator trim actuator position was found to be unreliable due to the cables being pulled by first responders. The flap motor was found separated, and the flap jackscrew was found in a position consistent with the flaps being in the retracted position. The flap jackscrew moved freely by hand when rotated.
The engine remained partially attached to the engine mount structure and exhibited thermal damage to the accessory housing area. All components were examined and no pre-accident failures were found. The propeller remained attached to the propeller flange. The blades indicated leading edge polishing and bending consistent with rotation at impact.
Medical Information
The Fresno County Coroner determined that the cause of the pilot’s death was “. . . multiple . . . injuries due to blunt impact.” The FAA’s Civil Aeromedical Institute (CAMI) performed toxicology tests. Carbon monoxide, cyanide, volatiles and drugs were tested, and there were positive results for unspecified levels of bupropion in the muscle and liver.
During his previous FAA medical exam, the pilot marked “NO” to all blocks in Section 18 of the application including, “Have you ever in your life been diagnosed with, had or do you presently have” . . . “c. Eye or vision trouble except glasses” and “d. Mental disorders of any sort, depression, anxiety, etc.”
Review of personal medical records from March 2010 through November 2013 revealed that the pilot had a history of high cholesterol, gout, high blood pressure and major depression in complete remission. Records from the pilot’s last visit on Nov. 23, 2013, identified his medications as simvastatin, allopurinol, lisinopril, hydrochlorothiazide and bupropion. On that date, the records noted, “mood, memory and judgment normal.”
Simvastatin is used to treat high cholesterol, and is marketed as Zocor. Allopurinol is used to treat gout, and is marketed as Zyloprim. Lisinopril and hydrochlorothiazide are used to treat high blood pressure, and are marketed as Prinivil and Esidrix, respectively. Bupropion is used to treat depression and help people quit smoking; it is marketed with the additional names Wellbutrin and Zyban.
According to additional records from the pilot’s optometrist, he began annual visits in May 2010 because he was seeing halos around stars at night. That exam identified bilateral cataracts with trace nuclear sclerosis (yellowing and opacification of the central zone of the lens) in the left lens and 1+ nuclear sclerosis in the right lens. At that time, his corrected distance visual acuity was 20/20 in both eyes; his corrected visual acuity remained unchanged on all following examinations. The pilot’s last eye exam was dated Nov. 14, 2013, and the optometrist recorded bilateral cataracts with 1+ nuclear sclerosis, bilateral vitreous floaters and a right vitreous opacity.
Analysis
The Safety Board concluded that the pilot’s FAA medical records showed he had not reported any medical conditions. However, according to the pilot’s personal medical records, he had elevated cholesterol, gout, high blood pressure and chronic depression that was in remission; all were adequately controlled and the medications being used were unlikely to impair the pilot’s performance.
Although the pilot’s corrected visual acuity remained 20/20 bilaterally, he had complained to his optometrist of vision problems with halos around stars. Annual exams documented progression of bilateral cataracts and vitreous opacities in the four years before the accident.
Cataracts can cause halos around points of light (glare) and degrade night vision. A witness, who was based at the pilot’s home airport, reported that the pilot recently had problems taxiing on a familiar lighted runway and taxiway at night.
The Board said that based on the pilot’s four-year history of progressive bilateral cataracts, complaints of halos around stars at night, prior difficulty operating the airplane at night on his lighted home airport runway, and his unsuccessful attempts to land on an unfamiliar runway at night, it was likely that cataracts degraded his ability to see clearly at night and resulted in his inability to safely operate the airplane during the accident sequence.
Thus the probable cause of this accident, said the Safety Board, was “the pilot’s failure to maintain adequate clearance from trees while on approach, which subsequently led to a loss of airplane control. Also causal was the pilot’s continued operation of the airplane at night with a diagnosed medical condition that degraded his night vision.”
My bottom line? Regardless of what you tell your AME, be sure you fess up with your general practitioner and specialists as you get older. Understand the limitations posed by your physical challenges and medications. If things are correctable, get them corrected. If things just can’t be fixed, adjust your personal hazard/risk mitigation program to suit the situation. Like the guy says — know yourself; know your limitations.
AFAP knowledge 