# NTSB CHI91DER10: Kolb Twinstar MK II, N503BP, Staples, MN, June 30, 1991

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Final report
- Date: June 29, 1991, 20:05 local (Jun 30, 1991, 01:05 UTC)
- Place: Staples, MN
- Coordinates: 46.360099, -94.800369 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=46.3601&lon=-94.8004&mi=10
- Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping)
- Highest injury: Serious injuries
- Injuries: 1 serious
- Status: Completed, report March 31, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 14856
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI91DER10
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/14856/pdf
- Page: https://openairdocs.org/ntsb/CHI91DER10

## Probable cause

THE DISCONNECTED ELEVATOR TRIM CABLE.  RELATED FACTORS ARE THE INADEQUATE MAINTENANCE/INSTALLATION, AND THE PILOT'S INABILITY TO MAINTAIN AIRCRAFT CONTROL.

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Airframe/component/system failure/malfunction, takeoff - initial climb
  - maintenance,installation - inadequate, pilot in command (contributing factor)
  - flt control syst,elevator trim/tab control - disconnected (cause)
  - aircraft control - not maintained, pilot in command (contributing factor)
- In flight collision with terrain/water, descent - uncontrolled

## Analysis

WITNESSES REPORTED THEY WATCHED THE ULTRALIGHT TAKE OFF AND NOTED THE ELEVATOR OSCILLATING RAPIDLY, 'FLUTTERING.' THEY STATED THE AIRCRAFT CLIMBED TO ABOUT 200 FEET ABOVE THE GROUND (AGL), THEN THE PILOT BEGAN A TURN BACK TOWARD THE AIRPORT.  ACCORDING TO ONE WITNESS:  'THE AIRPLANE STALLED, WENT INTO A SPIN AND CRASHED.'  THE ULTRALIGHT IMPACTED TERRAIN IN A MARSHY AREA LESS THAN ONE MILE FROM THE DEPARTURE AIRPORT. POST ACCIDENT INVESTIGATION REVEALED THE TRIM TAB CONTROL CABLE HAD UNSPOOLED FROM THE TRIM TAB WHEEL.

## Aircraft

- Registration: [N503BP](https://openairdocs.org/deregistered/N503BP-1993-01-28), registration cancelled 1993-01-28, S/N TS223 (OpenAirDocs)
- Reported make and model: Kolb Company TWINSTAR MK II (TWINSTAR M)
- Registry model: [Poage William Tipton TWINSTAR MK II](https://openairdocs.org/model/poage-william-tipton-twinstar-mk-ii) (registry code 056188M) (OpenAirDocs)
- Category: Ultralight, amateur-built
- Serial number: TS223
- Airframe hours: 20
- Engines: Rotax M503 48 horsepower reciprocating
- Damage: Destroyed
- Flight: Personal, Part 91
- Operator: William T. Poage
- Registered owner: William T. Poage
- Airworthiness certificate: Special, Experimental (Special)
- Last inspection: Annual, April 19, 1991, 20 hours before
- Airport: SAZ, Staples, runway 32, 3,304 × 75 ft

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 32; private; airplane ratings: single-engine land; medical: class 3, valid medical--w/ waivers/lim; seat: left; flight hours: 300 total, 250 as pilot in command, 2 in the last 90 days, 2 in the last 30 days

## Weather

- Conditions: Visual (VMC), Dusk
- Wind: 40° at 10 knots
- Visibility: 15 statute miles
- Lowest ceiling: 10,000 ft broken
- Temperature: 75 °F, dew point 66 °F
- Altimeter: 29.00 inHg
- Observed at: BRD, 33 nm away

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Accident 19910629024819A](https://openairdocs.org/incident/19910629024819A), Jun 29, 1991: Amtrkb TWINSTAR, Staples, MN, Destroyed. Elevator flutter on climbout. Tried turn back. Stalled. Vertical impact. Trim wheel assembly allowed cable come off

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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