Issue Number 251
May 2000
A Monthly Safety Bulletin from The Office of the NASA Aviation Safety Reporting System
P.O. Box 189, Moffett Field, CA 94035-0189

Readback/Hearback, Much To Be Heard on Both Sides

There has been much discussion lately about pilots' and controllers' respective responsibilities for accurate verbal communications. Several recent ASRS reports present suggestions aimed at improving communication on both sides. We begin with a Captain's account of a clearance misinterpretation that led to a rejected takeoff.

  • Tower gave us, Company X15, position and hold [on] Runway 12R "for spacing." As we set the brake we thought we heard, "Company X15 right turn, right turn you are cleared for takeoff." I responded, "Company X15 right turn, right turn cleared for takeoff Runway 12R." We next heard, "Tower, Company Y15, verify that clearance was for us." We aborted immediately (from taxi speed) and called "Company X15 aborting." Tower instructed us to clear to [the] right and taxi back to the end, which we did. Company Y15 took off, and then we did.

    It appears that we took their similar call sign. We made a mistake. Factors:
    • Taxiing out, we were told to anticipate a left turn. The "right turn, right turn" helped to suck us in.
    • We were not told "traffic departing crossing runway" when we were put in position.
    • (The Tower did not state the runway, to my knowledge.

  • After a similar incident years ago (I was the cleared one), I started always using call sign and runway on Tower frequency. If we all used call sign and runway on Tower frequency, would it not be a step in the right direction to avoid such incidents?

Including the runway in the takeoff clearance as well as crossing clearances would help prevents such incidents, too.

The Pause That ConfusesA popular punctuation joke presents a "Dear John" letter in two versions, each version consisting of the same words, but quite different meanings. Excerpts follow:

Version 1

    "...I have no feelings whatsoever when we're apart. I can be forever happy – will you let me be yours?"

Version 2

    "...I have no feelings whatsoever. When we're apart, I can be forever happy. Will you let me be?"

The analogy in pilot-controller verbal communications is the pause – where it falls in the transmission, and how long it lasts. A recent Captain's report to ASRS illustrates the confusion that can result when the timing of the pause is off.

  • Upon receiving takeoff clearance, Tower modified the SID to fly runway heading (010°). Upon climbing through 1,000 feet MSL, Tower instructed us to do the following:

    "[Aircraft call sign] Start your turn to heading 030° (same as SID) – pause/breath – at 4,000 feet contact [Departure] on 120.9."

    What the Tower meant to say was:

    "Start your turn to heading 030° at 4,000 feet. Contact [Departure] on 120.9."

    Depending on where the pause/breath was taken, the instructions from Tower have different implications. After contacting [Departure], they asked our heading and advised us of traffic...ahead. We acknowledged the traffic in sight and asked if they wanted us back on a 010° heading. Several seconds went by. Then [Departure] assigned us a heading of 350°, direct [fix] when able.

Im-PROP-er Engine Starts

Many small airplanes have impulse magnetos installed which use sensitive spring-loaded coupling to produce a series of sudden rotations – and hot sparks – during starting. If the magnetos are on, even the slightest manual turn of a prop may be enough to snap the magneto and start the engine, as this unlucky pilot discovered:

Any pilot hand-turning a prop should make sure the magnetos are in the off position. In addition, hand-propping is never a one-person job. A second person is always needed in the cockpit to apply brakes.

Legally Armed and DangerousASRS hears occasionally about passengers who are legally authorized to carry weapons on board aircraft, but who may not be up to the serious responsibilities involved. A recent report from an air carrier Captain explains:

As this crew discovered, armed passengers gripped by the fear of flying may not exercise the best judgment. Other flight crews who find themselves in this situation have the option of requiring the armed passenger to unload and check the gun as cargo, or if the nervous flyer refuses, to deplane both passenger and weapon.

"A Gaping Hole in Security Procedures"In March 1998, CALLBACK reported an incident involving a legally armed passenger – another white-knuckle flyer – who left his gun and holster in the aircraft lavatory during flight, where it was later discovered by a flight attendant. In a similar incident reported to ASRS, the forgetful passenger was not nervous – just inexcusably careless:

More on "Mechanics of the Human Mind"

An article in the February issue of CALLBACK (#248) described a GA pilot's disorientation during a gyro failure in instrument weather conditions. Distracted during the emergency by a spinning heading indicator and see-saw attitude indicator, he later reflected, "All my initial and recurrent partial panel training has been accomplished using suction cup style covers over the attitude and heading indicators. In this actual event, I found it difficult to ignore the erroneous information presented by these instruments."

A number of readers empathized with this pilot's predicament, and a few took us gently to task for not mentioning the obvious:

An elegantly simple solution that other pilots flying "actual" will want to consider.

ASRS Recently Issued Alerts On...
A reported charting error involving a Prohibited Area
CL65 stabilizer and mach trim failure during a takeoff
Non-compliance with Required Inspection Items (RIIs)
MD-80 in-flight loss of control following trim maintenance
Problems with a ATC Rapid Data Voice Switching system
March 2000 Report Intake
 Air Carrier/Air Taxi Pilots
 General Aviation Pilots