B737-400 flight crew detects smoke during climbout and isolates it to the first officer's left yoke ...

Narrative:

During climb both pilots could smell burning electrical insulation. I looked across the cockpit at the first officer when I noticed smoke rising from the left side of the first officer's yoke. The first officer was unable to see the smoke seeping through his fingers. The smoke was so thin that I could only see it when the sun shined on it. First officer noticed the left hand grip of his yoke was hot. We determined the smoke was coming from the lighted numerical thumb wheel installed on the yoke. We turned off all the instrument lighting in the cockpit and began the smoke; fire; or fumes in passenger cabin or flight deck checklist. Before reaching the step for bus transfer switch off the smoke and fumes had dissipated. The grip on the yoke was not as hot as when we first saw the smoke. We elected to discontinue the checklist since it appeared we had isolated the source and the smoke and fumes had dissipated. By this time; we were overhead ZZZ1 at 15;000 feet. We decided not to continue the flight and after consulting with dispatch; we diverted to ZZZ1. Performed normal descent and approach checklists to an uneventful landing. Because of the close proximity of the airport we did not take time to identify and pull circuit breakers. Did not exceed landing weight limitations. Maintenance revealed the light assembly in the yoke had failed; shorted; caused smoke and fumes; and the hot grip on the first officer's yoke.

Original NASA ASRS Text

Title: B737-400 flight crew detects smoke during climbout and isolates it to the First Officer's left yoke hand grip which is hot. All instrument lighting is turned off and the yoke begins to cool. Crew elects to divert to a suitable airport.

Narrative: During climb both pilots could smell burning electrical insulation. I looked across the cockpit at the First Officer when I noticed smoke rising from the left side of the First Officer's yoke. The First Officer was unable to see the smoke seeping through his fingers. The smoke was so thin that I could only see it when the sun shined on it. First Officer noticed the left hand grip of his yoke was hot. We determined the smoke was coming from the lighted numerical thumb wheel installed on the yoke. We turned off all the instrument lighting in the cockpit and began the SMOKE; FIRE; OR FUMES IN PASSENGER CABIN OR FLIGHT DECK Checklist. Before reaching the step for BUS TRANSFER Switch OFF the smoke and fumes had dissipated. The grip on the yoke was not as hot as when we first saw the smoke. We elected to discontinue the checklist since it appeared we had isolated the source and the smoke and fumes had dissipated. By this time; we were overhead ZZZ1 at 15;000 feet. We decided not to continue the flight and after consulting with Dispatch; we diverted to ZZZ1. Performed normal descent and approach checklists to an uneventful landing. Because of the close proximity of the airport we did not take time to identify and pull circuit breakers. Did not exceed landing weight limitations. Maintenance revealed the light assembly in the yoke had failed; shorted; caused smoke and fumes; and the hot grip on the First Officer's yoke.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1169538
Time
Date	201404
Local Time Of Day	0001-0600
Place
Locale Reference	ZZZ.TRACON
State Reference	US
Aircraft 1
Make Model Name	B737-400
Operating Under FAR Part	Part 121
Flight Phase	Climb
Flight Plan	IFR
Component
Aircraft Component	Electrical Wiring & Connectors
Person 1
Function	Captain Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	Pilot Flying First Officer
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Less Severe Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor

B737-400 flight crew detects smoke during climbout and isolates it to the first officer's left yoke hand grip which is hot. All instrument lighting is turned off and the yoke begins to cool. Crew elects to divert to a suitable airport.