Narrative:

Per our telecon this am I am enclosing the table TBD1 that proposes altering the TCASII warnings (visuals and aural). There is a reluctance by some pilots to expeditiously return to their clearance altitude after reacting to a TCASII RA that directs the pilot to deviate from his/her 'cleared' altitude. This reluctance to return to altitude also is expressed in a similar manner when responding to a TCASII 'climb' or 'descend' command, ie, if 1500 FPM is good 3500 FPM must be better. In an attempt to achieve a more accurate pilot response to TCASII commands, I am very happy to see the proposed addition of a green 'fly to' arc that is proposed, but extremely concerned that the proposed addition of the words 'maintain' and 'adjust' are subject to misinterp and ambiguity by pilots. I have been involved in the TCASII program since 1989. I have served as the TCASII program manager for X airlines since we started TCASII installation, and have read every pilot report (over 600) submitted by our pilots and have heard anecdotal evidence of a great many TCASII encounters. One incident sticks in my memory, that of a pilot relating to me his TCASII aural warning to 'dive, dive'! Upon being advised that the software cannot produce that particular aural warning, he informed me to 'check with bendix and see who put it in their machine, because that's what it said, 'dive, dive'! That is his perception of what the aural command he heard was (in all reality, it was close enough), and no amount of facts or data would persuade him he 'heard' differently. 'Perception is reality.' I have flown TCASII, I've been among large international groups that have debated TCASII, I've defended TCASII, and I believe in TCASII, but this change causes the pilot to hear a 'two word set' message. Either 'adjust,' 'maintain,' or 'monitor,' vertical speed, even through the word 'maintain' or 'adjust' is repeated after vertical speed. The command, in my mind, will do nothing to improve the accuracy of pilot compliance to the command, and will or could introduce a heretofore unknown reaction to the TCASII system. The pilot will not, in all likelihood, hear adjust, monitor, or maintain, he will only hear 'vertical speed.' enclosed is a letter that relates to the subject. I have attempted to contact him but we've played telephone tag so far. Please assist me in this matter as you are able. I am not adverse to sharing this information with any party that might be interested in the improvement of safety, be it in the human factors area or TCASII.

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Original NASA ASRS Text

Title: TCASII COMMENTS ABOUT PROPOSED AURAL TCASII CHANGES.

Narrative: PER OUR TELECON THIS AM I AM ENCLOSING THE TABLE TBD1 THAT PROPOSES ALTERING THE TCASII WARNINGS (VISUALS AND AURAL). THERE IS A RELUCTANCE BY SOME PLTS TO EXPEDITIOUSLY RETURN TO THEIR CLRNC ALT AFTER REACTING TO A TCASII RA THAT DIRECTS THE PLT TO DEVIATE FROM HIS/HER 'CLRED' ALT. THIS RELUCTANCE TO RETURN TO ALT ALSO IS EXPRESSED IN A SIMILAR MANNER WHEN RESPONDING TO A TCASII 'CLB' OR 'DSND' COMMAND, IE, IF 1500 FPM IS GOOD 3500 FPM MUST BE BETTER. IN AN ATTEMPT TO ACHIEVE A MORE ACCURATE PLT RESPONSE TO TCASII COMMANDS, I AM VERY HAPPY TO SEE THE PROPOSED ADDITION OF A GREEN 'FLY TO' ARC THAT IS PROPOSED, BUT EXTREMELY CONCERNED THAT THE PROPOSED ADDITION OF THE WORDS 'MAINTAIN' AND 'ADJUST' ARE SUBJECT TO MISINTERP AND AMBIGUITY BY PLTS. I HAVE BEEN INVOLVED IN THE TCASII PROGRAM SINCE 1989. I HAVE SERVED AS THE TCASII PROGRAM MGR FOR X AIRLINES SINCE WE STARTED TCASII INSTALLATION, AND HAVE READ EVERY PLT RPT (OVER 600) SUBMITTED BY OUR PLTS AND HAVE HEARD ANECDOTAL EVIDENCE OF A GREAT MANY TCASII ENCOUNTERS. ONE INCIDENT STICKS IN MY MEMORY, THAT OF A PLT RELATING TO ME HIS TCASII AURAL WARNING TO 'DIVE, DIVE'! UPON BEING ADVISED THAT THE SOFTWARE CANNOT PRODUCE THAT PARTICULAR AURAL WARNING, HE INFORMED ME TO 'CHK WITH BENDIX AND SEE WHO PUT IT IN THEIR MACHINE, BECAUSE THAT'S WHAT IT SAID, 'DIVE, DIVE'! THAT IS HIS PERCEPTION OF WHAT THE AURAL COMMAND HE HEARD WAS (IN ALL REALITY, IT WAS CLOSE ENOUGH), AND NO AMOUNT OF FACTS OR DATA WOULD PERSUADE HIM HE 'HEARD' DIFFERENTLY. 'PERCEPTION IS REALITY.' I HAVE FLOWN TCASII, I'VE BEEN AMONG LARGE INTL GROUPS THAT HAVE DEBATED TCASII, I'VE DEFENDED TCASII, AND I BELIEVE IN TCASII, BUT THIS CHANGE CAUSES THE PLT TO HEAR A 'TWO WORD SET' MESSAGE. EITHER 'ADJUST,' 'MAINTAIN,' OR 'MONITOR,' VERT SPD, EVEN THROUGH THE WORD 'MAINTAIN' OR 'ADJUST' IS REPEATED AFTER VERT SPD. THE COMMAND, IN MY MIND, WILL DO NOTHING TO IMPROVE THE ACCURACY OF PLT COMPLIANCE TO THE COMMAND, AND WILL OR COULD INTRODUCE A HERETOFORE UNKNOWN REACTION TO THE TCASII SYS. THE PLT WILL NOT, IN ALL LIKELIHOOD, HEAR ADJUST, MONITOR, OR MAINTAIN, HE WILL ONLY HEAR 'VERT SPD.' ENCLOSED IS A LETTER THAT RELATES TO THE SUBJECT. I HAVE ATTEMPTED TO CONTACT HIM BUT WE'VE PLAYED TELEPHONE TAG SO FAR. PLEASE ASSIST ME IN THIS MATTER AS YOU ARE ABLE. I AM NOT ADVERSE TO SHARING THIS INFO WITH ANY PARTY THAT MIGHT BE INTERESTED IN THE IMPROVEMENT OF SAFETY, BE IT IN THE HUMAN FACTORS AREA OR TCASII.

Data retrieved from NASA's ASRS site as of July 2007 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.