Harris BD-10 N9WZ

Summary

On 31 December 1994 at about 00:30 local time, a Harris BD-10 registered N9WZ, operated by Peregrine Flight International, was involved in an accident near Gardnerville, Nevada, United States. One person was on board and one died. The aircraft was destroyed. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

31 December 1994 at 00:30

Classification

Accident

Location

Gardnerville, Nevada, United States

Coordinates

Not recorded

Aircraft

Harris BD-10

Registration

N9WZ

Category

Airplane

Engines

1

Operator

Peregrine Flight International

Operating rule

Part 91: General Aviation

Purpose of flight

Unknown

Phase of flight

Not recorded

Route

Minden → Unknown

Aircraft damage

Destroyed

Weather

VMC

Light

Day

NTSB number

LAX95LA067

1 person died.

the in-flight overload failure of the left vertical stabilizer spars, at force levels substantially below the predicted ultimate failure loads, due to inadequate substantiation by the designer.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

THE FLIGHT'S TEST CARD CONCERNED EXPANSION OF THE SPEED ENVELOPE FROM 370 TO 380 KIAS. ON AN EARLIER TEST FLIGHT AT 350 KIAS, THE SIDE LOAD FORCES ON THE VERTICAL STABILIZERS REACHED A COMPANY IMPOSED LIMIT OF 40 PERCENT OF THE ULTIMATE FAILURE LOAD DETERMINED BY THE DESIGNER. DURING THE RUN BETWEEN 375 AND 380 KNOTS, THE AIRCRAFT PITCHED VIOLENTLY NOSE UP FOLLOWED BY A GENERAL BREAKUP. THE COMPANY SAID THE ORIGINAL BEDE BUILT BD-10 PROTOTYPE SUSTAINED A VERTICAL STABILIZER FAILURE DURING FLIGHTS AT THE 1994 RENO AIR RACES. BEDE SUBSEQUENTLY DESIGNED A FIX WHICH STRENGTHENED THE VERTICAL TAILS. GROUND SUBSTANTIATION LOAD TESTS TO FAILURE WERE CONDUCTED BY BEDE, AND THE RESULTING YIELD FAILURE LOAD LIMIT WAS PROVIDED TO THE COMPANY, WHICH USED THE NUMBERS TO ESTABLISH THE 40 PERCENT FLIGHT TEST LIMIT. THE NEW FIX WAS INCORPORATED INTO THE ACCIDENT AIRCRAFT. WRECKAGE EXAMINATION REVEALED THAT THE AIRPLANE'S VERTICAL TAILS SUSTAINED STRUCTURAL OVERLOADS AND SEPARATED FROM THE AIRCRAFT IN FLIGHT. THE INTACT LEFT VERTICAL TAIL ASSEMBLY WAS FOUND EARLY IN THE WRECKAGE PATH AND EXHIBITED A CLEAN, ALMOST INSTANTANEOUS FAILURE LOAD WITH RIGHT BENDING AT THE SPAR TO FUSELAGE ATTACH POINTS. A PRODUCTION CONFIGURATION LEFT SIDE EMPENNAGE WAS BUILT, PUT IN A TEST FIXTURE, AND THE VERTICAL TAIL LOADED TO FAILURE. THE FAILURE MODE AND SEPARATION POINT WAS THE SAME AS THAT SEEN ON THE ACCIDENT AIRCRAFT LEFT VERTICAL TAIL ASSEMBLY. THE VERTICAL STABILIZER SPARS BEGAN TO YIELD AT 40 PERCENT OF THE FAILURE LOAD LIMIT SUPPLIED BY BEDE. SPAR FAILURE OCCURRED AT 65 PERCENT.

Quoted verbatim from the NTSB record.