Issue Number 234
December 1998
A Monthly Safety Bulletin from The Office of the NASA Aviation Safety Reporting System
P.O. Box 189, Moffett Field, CA 94035-0189

"The Ice Cometh" Icicles

This is the time of year when many pilots are gearing up for the increased likelihood of encountering in-flight icing. Our first reporter believed that an airplane "certified for flight into known icing" could handle a routine IFR flight.

[On post-flight], there was about one-quarter inch of ice remaining on the nose, spinners, upper portion of the tail and other unprotected areas. I assume significant ice was shed while descending. I have become an even more cautious flight planner. I now know first-hand that icing conditions are unpredictable and how severe localized icing can be -- it can quickly overpower a "known icing" aircraft.

IceboundLoss of aircraft control due to the weight of ice and the disruption of airflow over the wings and elevator surfaces is only one part of the icing story. Ice accumulation can also cause jamming or malfunction of controls and components, as an air carrier First Officer reports:

The reporter surmised that the previous night's rain and wind had blown water into the control unit housings, where the water froze, causing the controls to jam.

Get-There-ItisA General Aviation pilot debated filing an IFR flight plan for a pleasure flight in mixed VMC/IMC. The reporter even considered canceling the flight because of the weather, but admits that "my judgment was clouded by 'get-there-itis' combined with beckoning patches of blue sky."

The reporter points out several lessons to be learned from this incident: Check the pitot heat before any flight which has the potential to be in IMC, and carefully monitor weight and balance for aft-of-limit conditions that may hamper stall recovery. Finally, avoid the beckoning lure of those "blue patches" between clouds.


Communications between pilots and controllers is secondhand when aircraft are beyond the range of ATC's radio coverage. The middleman in the process is a commercial radio service (also known as General Purpose radio), which uses the high frequency ranges. A Center controller working the Gulf of Mexico describes the confusion that can result when communication is indirect:

A number of pilots also report communications difficulties in the Gulf and on Oceanic routes. An air carrier Captain, enroute to the U.S. over the Gulf of Mexico, credits TCAS for providing information when ATC couldn't:

Both pilots and controllers can help minimize confusion and misunderstandings by following good basic radio procedures. In addition, when the usual communication methods fail to get a response, relaying position reports and other information via another aircraft may be an option.

Service Agent Inspecting BaggageCustom-Airy ServiceInability to establish communications was equally distressing for a General Aviation pilot, who learned the consequences of altering the flight-planned flight without verifying the change with the appropriate authorities.

The Entry Requirements Section of the Aeronautical Information Manual explains the procedures for entering the U.S. and clearing Customs. Pilots must land at the Customs location they list on their flight plan, or provide advance notice directly to Customs regarding the location of intended arrival.

Managing Cockpit Interruptions and Distractions

This pilot's report of a taxiing mishap was one of 107 ASRS incidents recently reviewed by human factors scientists at NASA Ames, as part of a research study on why flight crews are vulnerable to errors caused by preoccupation, distraction, and interruptions. The results of the study are summarized in an article that appears in the latest issue (#10) of the ASRS Directline publication, available from the ASRS Web site:

(available December 15)

In a large majority of the ASRS incidents reviewed, pilots became distracted or preoccupied with competing tasks. These tasks fell into four broad categories:

(1) communications (among crew or via radio); (2) head-down work (programming the FMS or reviewing approach plates); (3) searching for VFR traffic; (4) responding to abnormal situations.

The authors of the NASA study identify preventive actions and strategies to reduce flight crew vulnerability to distraction and preoccupation. Their article also includes a down-to-earth explanation of the two systems humans use to perform tasks-the conscious and automatic systems-and why some cockpit activities (conversation, for example) may demand more conscious effort than others.

ASRS Recently Issued Alerts On...
BA-32 hydraulic pressure loss
CL-601 brake failure on landing
Restraint procedures during air transport of prisoners
Cargo door failure and rapid decompression on a DA-20
TCAS II alerts attributed to a transponder on a Texas building
October 1998 Report Intake
 Air Carrier/Air Taxi Pilots
 General Aviation Pilots