# NTSB CHI94LA299: Robert Eldon Idler TIERRA-2, N6161Q, Prole, IA, August 26, 1994

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Limited investigation · Final report
- Date: August 25, 1994, 19:15 local (Aug 26, 1994, 00:15 UTC)
- Place: Prole, IA
- Coordinates: 41.380817, -93.729965 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=41.3808&lon=-93.7300&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 2 minor
- Status: Completed, report February 14, 1995
- Report: Approved by Office Director
- NTSB case key (mKey): 9655
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI94LA299
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/9655/pdf
- Page: https://openairdocs.org/ntsb/CHI94LA299

## Probable cause

the airplane's encounter with the outflow (gust front) from an approaching thunderstorm.  Factors were the pilot's inaccurate evaluation of the gust front location, and the inability of the airplanes flight control system to compensate for the rolling moment.

## Sequence of events

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

- In flight encounter with weather, climb - to cruise
  - weather condition - thunderstorm,outflow (cause)
  - weather evaluation - inaccurate, pilot in command (contributing factor)
- Loss of control - in flight, climb - to cruise
  - aircraft performance,turn capability - inadequate (contributing factor)
- In flight collision with terrain/water, descent - uncontrolled
  - object - tree(s)

## Analysis

DURING CRUISE FLIGHT, THE TWO-SEAT REGISTERED ULTRALIGHT AIRCRAFT ENCOUNTERED THE GUST FRONT FROM AN APPROACHING THUNDERSTORM WHICH WAS LOCATED 7 TO 15 MILES AWAY.  THE ULTRALIGHT ENTERED AN UNCOMMANDED RIGHT DESCENDING BANK, WHICH THE PILOT COULD COULD NOT ARREST WITH FULL OPPOSITE AILERON INPUT.  THE ULTRALIGHT IMPACTED TREES AND WAS DESTROYED.

## Factual narrative

On August 25, 1994, at 1915 hours central daylight time, a Tierra-2, 2 seat registered ultralight aircraft, N6161Q, operated by Robert Idler of West Des Moines, Iowa, impacted wooded, hilly terrain 8 miles southwest of Des Moines, Iowa, and was destroyed. The Airline Transport rated pilot and passenger received minor injuries.  No fire occurred.  Visual meteorological conditions existed at the time of the accident and no flight plan was filed.

The flight operated under 14 CFR Part 91, originated from Chandler Field on the Gene Wilson Farm in rural Prole, Iowa, at 1900 central daylight time.  The pilot reported that he took off in clear weather and was overrun by the gust front of an approaching thunderstorm which was located between 7 and 15 miles away.  The aircraft entered an uncommanded right descending turn, which the pilot reported he was unable to counter with full left aileron input.  He also reported that the engine operated normally until the aircraft impacted trees.

## Aircraft

- Registration: [N6161Q](https://openairdocs.org/deregistered/N6161Q-1997-01-15), registration cancelled 1997-01-15, S/N 1 (OpenAirDocs)
- Reported make and model: ROBERT ELDON IDLER TIERRA-2
- Registry model: [Eilts David/Idler Robert TIERRA II](https://openairdocs.org/model/eilts-david-idler-robert-tierra-ii) (registry code 05620XM) (OpenAirDocs)
- Category: Airplane, amateur-built
- Serial number: 1
- Airframe hours: 97
- Engines: ROTAX 532 65 horsepower reciprocating
- Damage: Destroyed
- Flight: Personal, Part 91
- Registered owner: Robert Idler
- Airworthiness certificate: Special, Experimental (Special)
- Last inspection: Annual, January 4, 1995, 42 hours before
- Departed: NONE, DES MOINES, IA
- Airport: Chandler Field

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 41; airline transport, flight instructor; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, valid medical--no waivers/lim.; seat: left; flight hours: 9,111 total, 27 in this make and model, 8,904 as pilot in command, 97 in the last 90 days, 36 in the last 30 days, 1 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 88 °F

## 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 19940825023999A](https://openairdocs.org/incident/19940825023999A), Aug 25, 1994: Amtrte TIERRA2, Prole, IA, Destroyed. Encountered severe gust from nearby thunderstorm. Entered uncommanded unrecoverable bank. Impacted trees. Destroyed

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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