- Date
- June 24, 2004, 15:10 local (21:10 UTC)
- Place
- Bozeman, MT
- Injuries
- 2 uninjured
- Damage
- Substantial damage
- Phase of flight
- Landing
- Aircraft
- N4585FCessna 185F
- Weather
- Visual (VMC) · Day
- Status
- Completed · report September 13, 2005
- Report
- Approved by Office Director
- Parties
- Helena FSDO
- FAA report
- 20040624015999A
- Case key
- 59530
From the NTSB’s public API. By law, NTSB reports can’t be used as evidence in lawsuits over the accident.
On this page
Probable cause
The failure of the right main gear brake disk attach flange during the landing roll, due to fatigue cracks emanating from numerous corrosion pits present on the surface of the disk, leading to the right brake becoming totally inoperative, and resulting in a rapid inadvertent ground-loop. Factors include hard braking applied by the pilot in order to turn off the active runway at an early taxiway, and considerable corrosion on the surface of the brake disk flange.
Sequence of events
NTSB’s coding before 2008: each occurrence and phase of flight, and the causes and factors under it. The codes are defined in NTSB’s coding manual.
Analysis
During the landing roll, the pilot was applying heavy braking in order to turn off the runway at taxiway Echo, when the aircraft suddenly and rapidly ground-looped to the left. An initial post-accident inspection of the aircraft revealed that the right main gear brake rotor assembly had torn lose from the wheel itself, rendering the right wheel brake totally inoperative. The wheel hub and brake disk assembly were shipped to the NTSB Materials Laboratory, where it was determined that the brake disk attachment flange failed in fatigue in the bend around the attachment flange. The brake disk showed a substantial amount of general corrosion, and although the attachment flange met the minimum thickness requirements, most of its surface was covered by corrosion and corrosion pitting. The fatigue crack propagation that eventually lead to the failure had originated in one of these corrosion pits.
Factual narrative
On June 24, 2004, approximately 1510 mountain daylight time, a Cessna 185F, N4585F, ground-looped during the landing roll at Gallatin Field, Bozeman, Montana. The private pilot and his passenger were not injured, but the aircraft, which is owned and operated by the pilot, sustained substantial damage. The 14 CFR Part 91 personal pleasure flight, which departed from an unknown location, was being operated in visual meteorological conditions. No flight plan had been filed.
According to the pilot, during the landing roll he was applying normal heavy braking in order to turn off the runway at taxiway Echo, when the aircraft suddenly and rapidly ground-looped to the left. An initial post-accident inspection of the aircraft revealed that the right main gear brake rotor assembly had torn lose from the wheel itself, rendering the right wheel brake totally inoperative.
The wheel hub and brake disk assembly were shipped to the NTSB Materials Laboratory, where it was determined that the brake disk attachment flange failed in fatigue in the bend around the attachment flange. The brake disk showed a substantial amount of general corrosion, and although the attachment flange met the minimum thickness requirements, most of its surface was covered by corrosion and corrosion pitting. The fatigue crack propagation that eventually lead to the failure had originated in one of these corrosion pits.
The pilot did not return a completed NTSB Form 6120.1/2, so the total flight time information for this report was taken from data recorded on his last FAA medical examination.
Aircraft
- Registration
- N4585F
- Reported as
- Cessna 185F
- Category
- Airplane
- Serial number
- 1851092
- Engine
- Continental IO-520-D, 300 horsepower, reciprocating
- Damage
- Substantial damage
- Flight
- Personal · Part 91
- Registered owner
- Kenneth D. Chapman
- Airworthiness certificate
- Standard, Normal
- Destination
- BZN · Bozeman, MT
- Airport
- KBZN · Gallatin Field, runway 30, 9,003 × 150 ft, asphalt
Matched to the registry by N-number and the event date; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.
Flight crew
As NTSB recorded them. NTSB leaves out names.
- Role
- Pilot
- Age
- 58
- Injuries
- None
- Certificate
- Private
- Airplane ratings
- Single-engine land
- Medical
- Class 3, With waivers/limitations
- Seat
- Left
- Flight hours
- 2,450 total
Weather
- Conditions
- Visual (VMC) · Day
- Visibility
- 20 statute miles
- Lowest ceiling
- None
- Temperature
- 75 °F
FAA reports on this event · 1
The FAA’s own accident and incident reports, matched to the aircraft by N-number and date.
Other investigations on N4585F · 1
Matched to the same aircraft by N-number and date.