1972_美国_AAR7207.pdf

8 NAT-ONAL TRANSPORT-ON SAFETY BOARD

PB 208 223

AIRCRAFT INCIDENT REPORT

TRANS WORLD AIRLINESBoeing 707, N6729TW andAMERICAN AIRLINESBoeing 707, N8432Near Phillipsburg, PennsylvaniaJune 11, 1971

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Washington, D. C. 20591

REPORT NUMBER: NTSB.AAR-72-7

SA-None

File No. 1-0010

AIRCRAFT INCIDENT REPORT

TRANS WORLD AIRLINES

Boeing 707, N6729TW and

AMERICAN AIRLINES

Boeing 707, N8432

Near Phillipsburg, Pennsylvania

June 11, 1971

Adopted: DECEMBER 29, 1971

NATIONAL TRANSPORTATION SAFETY BOARD

Washington, D. C. 20591

REPORT NUMBER: NYSB-AAR-72-7

TECHNICAL REPORT STANDARD TITLE PAGE

NTSB Form 1765.2 (11/70)

TRANS WORLD AILINES BOEDIG 707, N6729TW AND AMERICAN AILINES BOEDIG 707, N8432 NEAR PHILIPSBURO, PENNSYLVANIA, JUNE 11, 1971

TABLE OF CONTENTS

SPECIAL NOTICE

This report contains the essential Items of Information relevant to the probable causes and safety messages to be derived from this Incident. However, for those having a need for more detailed Information, the original factual report on the Incident is on file in the Washington office of the National Transportation Safety Board. Upon request the report will be reproduced commercially at an average cost of 154 per page for printed matter and 754 per page for photographs, plus postage. (Minimum charge $1.00.)

Cples of material ordered will be called from the Washington business firm that holds the current contract for commercial reproduction of the Board's public files. Billing is also direct to you by the same firm.

Orders for this material will also involve a $2.00 user service charge by the Board for special service. This charge is in addition to the bill from the commercial reproduction firm.

Requests for reproduction should be forwarded to the:

NATIONAL TRANSPORTATION SAFETY BOARD Office of General Manager Accient Inquirles & Records Section Washington, O. C. 20591

File No. 1-0010

NATIONAL TRANSPORATION SAFETY POARD WASHINGTON, D. C. 20591 AIRCRAFT INCIDENT REPORT

Adopted: December 29, 1971.

TRANS WORLD AIRLINES BOEING 707, N67291W AND AMERICAN AIRLINES BOEING 707, N8432 EAR PHILIPERUNG, PENNSYLVANIA, JUNE 11, 1971.

SYNOPSIS

A Trans World Airlines (TWA) Boeing 707, N6729IW, and an American Airlines Boeing 707, N8432, narrowly avoided a midair collision at approximately 35,000 feet near Philipsburg, Pennsylvania, on June 11, 1971, while they were operating within positive control airspace under the control jurisdiction of the New York Air Route Traffic Control Center. As a result of the violent evasive maneuver executed by the captain of the TWA B-707, three passengers and the flight engineer incurred minor injuries. None of the occupants of the other aircraft, whose crew was unaware of the occurrence until some time later, was injured. There was no damage to either aircraft, both of which proceeded routinely to their respective destinations.

The National Transportation Safety Board determines that the probable cause of this incident was misidentification by a New York Center controller of the radar target of TW Flight 31, which resulted in inappropriate control action in respect to AA Flight 151 and which placed the two flights on a collision coarse at the same altitude.

The Safety Board recommends that:

The Federal Aviation Administration take appropriate action to assure that all adr traffic control personnel are made aware of this misidentification incident so that increased vigilance may result and serve to preclude the recurrence of similar incidents.

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INVESTIGATION

Trans World Airlines N6729W, Flight 31, (TW31) was a regularly scheduled passenger flight between Philadelphia, Pennsylvania, and San Francisco, California. The aircraft departed the late at 0930, 1/on an instrument flight rules (IFR) clearance "as filed, 2/Limerick four departure, flight plan route, maintain 8,000, expect: Flight Level (FL) 350 after Pottstorm." Takeoft was at 1002, and the flight was subsequently cleared to climb to 17,000 feet, then FL230, then FL260 on a heading of 330 degrees, then direct to Philipsburg (PSB) and on up to FL350.

As flight neared PSB it was instructed by the New York Air Route Traffic Control Center (NY CNTR) to contact Cleveland Center. At this point the first officer was flying the aircraft, and when they were about 9.5 rautical miles east of PSB in level cruise at FL350, the captain eaw the first officer's windshield "fill" with an American Airlines B-707 approximately 500 feet away and slightly above, flying approximately 90° to the left of TW31's course. The captain reacted instantly by pushing forward on the yoke. He estimated that the closest point of approach of the two aircraft was 50 feet.

As a result of the evasive maneuver, three passengers and the flight engineer of TW31 incurred minor injuries.

American Airlines N8432, Flight 151 (AA151), was a regularly scheduled passenger flight between Beton, Massachusetts, and Honolulu, Hawaii, with an intermediate stop in St. Louis, Missouri. The flight departed at 0937 and was proceeding in FL350 along J49 between Hancock, N.Y., and Philipsburg (PSB) when the NY CNTR directed the flight to turn left to a heading of 190° and to change to another NY CNTR frequency. Communications were established on the new frequency at 1024 and the captain (who was handling communications while the first officer was flying the aircraft) reported turning to the new heading at FL350. He then asked whether the vector was for spacing behind traffic and, after receiving an affirmative reply, requested a clearance to climb to FL390. The controller was unable to authorize the requested altitude because of traffic "at (FL) 370 right with you."

AA151 was then cleared to proceed direct to P3B (at 1025:35) and at 1026:45 was instructed to maintain a 270° heading to intercept J78 (the planned route of flight after P3B).

2/ All times used herein are eastern standard, based on the 24-hour clock.

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At 1028, TW31 reported NY CNTR that they had nearly hit AAI51. This report was the first knowledge that any of AAI51's crew had of the occurrence. The flights subsequently communicated with one another on 129.5MHz, after they had changed to the Cleveland Center frequency for traffic control purposes. Both flights proceeded to their destinations without further incident.

Sector 3 of the New York Air Route Traffic Control Center was responsible for traffic control in the airspace within which this incident occurred. The personnel assigned to Sector on June 11, 1971, were: a developmental radar controller (R3T) 3/, a monitor controller responsible for the actions of the developmental controller (R3M), a radar handoff controller (H3), and a sector coordinator.

ATC HANDLING OF TW31

The Cleveland Center Sector which adjolins NY CNTR Sector 3 is stratified into three layers, with each Subsector having its own set of controllers physically displaced from each of the other Subvectors. The altitudes which they control and the appropriate beacon code assignments for their traffic are:

On the NY CNTR side of the boundary, the airspace from FL180 up to FL600 is all contained within Sector 3 and there are no Subvectors. The three aforementioned beacon codes are employed on the same altitude basis. Aircraft operating between FL180 and FL230 use code 1300; between FL240 to FL330, code 2100; and traffic above that level, code 2300.

At 1024:25 the NY in dar landoff controller attempted a handoff of TW31 to the Cleveland Center. At that time the aircraft's target was 20 miles east of P3B. The receiving controller in Cleveland stated that he did not see the target. The radar handoff controller in NY replied that TW31 was right on the airway and his Cleveland counterpart responded: "Wait a minute, there's a guy coming on now "..." At that point the Cleveland Center established radar contact with TW31. At 1026:05, the NY developmental radar controller instructed TW31 to contact Cleveland Center on 133.3MHz.

3. A controller in training status as far as the position to which he is assigned is concerned.

$$ -l_4 = $$

At 1026:15 TW31 contacted Cleveland's Lorain Subsector radar controller and reported at FL350. The captain then reported the near midair collision and was advised of the flight identification of the American Airlines B-707. The occurrence was reported by the Cleveland Sector coordinator to the NY CNTR radar handof controller, who, in turn, asked that TW31 be returned to NY CNTR frequency for a minute. This was approved and the Cleveland radar controller instructed TW31, "change back to the NY CNTR on 127,95 and tell them about the evasive action you had to take. They had both airplanes."

TW31 contacted NY CNTR again at 1028:35 and, after activating the identification feature on their transponder, inquired whether AA151 had been displayed on the NY CNTR's radar. The NY CNTR replied in the affirmative. TW31 recited the events surrounding the incident and its location. The monitor controller's response was: "Yes sir, I see what happened here . . ." At this point, he instructed AA151 to change to Cleveland Center on 133.3MHz. However, before AA151 left 127.95-MHz., TW31 asked AA151 to converse on 129.5MHz. A transcription of the ensuing conversation appears in Appendix A to this report.

ATC HANDLING OF A A151

At 1023:20, AA151 was proceeding southwestward on J49 toward FSB at FL350. Four seconda earlier TW31 had reported level at FL350 headed for P3B. The NY CNTR Sector 29 handoff controller called the NY Sector 3 controller and advised him of AA151's location and flight level, since the aircraft was approaching the inter-sector boundary. The Sector 3 controller responded that there was another aircraft at FL350 25 miles east of P3B (purportedly the position of TW31's target). The Sector 291/ controller advised that he had no means of resolving the impending traffic confliction because of other traffic at FL310 and FL390. The Sector 3 controller suggested placing AA151 on a 190° heading (in order that the flight might be vectored to a point about 10 miles or so in trail behind TW31). He stated further that Cleveland Center would not accept aircraft at "the wrong altitude" (FL330 or FL370, utilized primarily by opposite direction traffic). This resolution of the problem was accepted by the H29 controller and an appropriate vector and frequency change was issued to AA151.

When AAI51's target was at a suitable distance behind that which was believed to be TW31, AAI51 was instructed to proceed direct to PSB. During the early stages of the right turn to this direct course, the two aircraft nearly collided.

4/3 sector 29 is adjacent to and northeast of Sector 3-PSB.

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ATC HANDLING OF N9HOBS

N940RS was a Gulfstream II er route from Allentown, Pennsylvania, to Detroit, Michigan. At 1012:25, the New York Center Sector 3 radar handoff controller accepted a handoff of N940BS when the aircraft was 9 miles west of Allentown heading direct to Philipsburg and climbing to its flight planned cruising level of 22,000 feet (FL220). At 1015:25, N940BS contacted the Sector 3 developmental radai controller and reported leaving FL190 for FL220. During this same time period, the Sector 3 controllers were handling another westbound aircraft headed toward Philipsburg. That aircraft was TW31.

Meteorological conditions are not considered pertinent to this incident.

All radio aids to navigation utilized by the aircraft discussed in this report were operating without reported difficulty, with one exception. The Keating, Pennsylvania, VORTAC was scheduled to be shut down for maintenance from 1000 to 1600. Appropriate coordination had been effected prior to the issuance of a Notice to Airmen concerning this shutdown. The information was furnished to the assistant chief on watch at the Cleveland Center; however, he failed to pass it on to the sectors concerned with traffic destined to utilize that VORTAC.

The flight data recorder from AA151 showed no erractic or sudden deviations during the period of time in which this incident occurred. All parameter traces were recording legibly and the foil was undamaged.

TW31's flight data recorder was likewise found to be operating properly during this time period. The heading trace showed a value of 288 l 1° for 1 minute prior to the commencement of the evasive maneuver. This maneuver was evidenced by a change in the vertical acceleration (g) value from a normal / 1.00g, in the negative direction to 10.02g, then positively to TW31 /1.7h, and subsequently back to 11.00g. There was no change in heading value during this "push-over" maneuver.

The cockpit voice recorder (CVR) from TW31 was not examined, since it was allowed to continue to operate subacquent to the incident for the remainder of the flight to San Francisco, thereby causing all recording prior to 30 minutes before engine shutdown to be erased.

The crew of AA151, after having been made aware of the near collision as a result of conversation with 1W31, pulled the circuit breaker on their CVR in order to preserve the data recorded thereon for later retrieval and examination. The CVR was removed from the aircraft at St. Louis and shipped to the Board in Washington, D. C., for examination and tape readout.

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ANALYSIS

This incident is not typical of most in that the causal factors do not involve the interrelationship of man, machine, and environment. On the contrary, the sequence of events which led to a near collision was dependent upon the acts of commission and commission by pen.

All of the controllers involved in the handling of the aircraft discussed herein characterized their workload as moderate. None of them had been on duty for longer than $3\frac{1}{2}$ hours on June 11, 1971, and their rest periods since their last duty tour hard been adequate.

The flightcrew participants in this dynamic situation had acted on the instructions or clearances issued by the controllers, which result in the near miss.

The failure of the Cleveland Center supervisor to relay to the cognizant sectors the data concerning the impending maintenance shutdown of the Keating VORTAC compounded the control problems. Had the controller involved been aware of this shutdown, he could have issued alternative rovtings to aircraft overflying Keating, or, at least, would have been aware of the reason for aircraft course deviations end inquiries in the vicinity of Keating.

There is no doubt that the NY CNTR developmental radar controller established positive identity in an appropriate manner in respect to the radar targets of TV31 and another westbound aircraft (N940RS) when they entered the cast end of his Sector 3 airspace. At this point the aircraft were separated from one another geographically, with the target of closer to PSB. Their appearances on the sector frequency were within 40 seconds of one another, with both aircraft climbing, TW31 initially to FI230 and N940PS to FI220, his final altitude.

About 2 minutes thercafter, a problem arose at the western end of the sector with respect to two other aircraft. While the three Sector Controllers focused their attention on this near confliction, the "shrimpoats" 5/ on TW31 and NW40RS were reversed. The identity reversal can be attributed to the fact that NW40RS had reached cruising altitude while TW31 was still climbing, thus creating a marked difference in ground speeds which caused NW40RS to pass TW31. When the controller resumed surveillance of that portion of his display the relative positions of the targets were reversed.

He now mistakenly considered the lead target to be TW31 and the following target to be N940R3, about 12 miles in trail. Consequently, when the necessity arose to vector AAL51 about 10 miles in trail behind

1. A plastic marker used to indicate the location and identity of a radar target on a horizontal radar display.

TW31, what actually occurred was that AAI51 was vectored about 10 miles behind N40RS and right across the flight path of TW31 at the same altitude.

Apart from the obvious means of preventing a recurrence of this type of hazardous situation, that is, by the constant retention of radar target identity, one is compelled to ponder what other means might be employed to avoid such mistakes in the future. Phrased differently, what might others have done to assist the Sector 3 controllers in recognizing their error? In this context, it should be borne in mind that once the identities had been reversed, with the targets more than 10 miles apart on an east-west line, the data regarding TW31's purported location which was provided to the Cleveland Center in the course of the handoff could not possibly have corresponded to the Cleveland controller's observed position of the target. Furthermore, because of the Cleveland Center's stratification and concomitant radar beacon code assignments only the targets of TW31 and AAI51 would have been displayed on the CLE Lorain Subsector. The target of N940BS would have been visible only to the Clarion Subsector controller. The Lorain Subsector handoff controller should have recognized the discrepancy between the stated and observed positions of the target being pointed out as TW31, and should have refused to accept the handoff until a more accurate assessment of TW31's position was accomplished. This action, if taken, would have prevented the near miss. The ultimate responsibility for maintaining appropriate radar target identity in this instance, however, reposed with the monitor controller at the NY CNTR.

The Board has not emphasized in this report the application of the principle of "see-and-avoic," since this incident occurred at FL350, within positive control airspace. In this environment, a pilot cannot, because of operational and physiological limitations, depend on visual detection of other aircraft, albeit this case does illustrate that visual alertness helped to avoid an accident. The rationale used by the Federal Aviation Administration for the establishment of positive control airspace was based on the fact that because of these limitations to flightcrews' capabilities to "see-and-avoic," an environment must be created in which all flight operations are known to, and under the control of, air traffic control.

Probable Cause

The National Transportation Safety Board determines that the probable cause of this incident was the misidentification by a New York Center controller of the radar target of TW Flight 31, which resulted in inappropriate control action in respect to AA Flight 151 and which placed the two flights on a collision course at the same altitude.

$$ \sim \delta = $$

Recommendation

The Safety Board recommends that:

The Federal Aviation Administration take appropriate action to assure that all air traffic control personnel are made aware of this misidentification incident so that increased vigilance may result and serve to preclude the recurrence of similar incidents.

BY THE NATIONAL TRANSPORTATION SAFETY BOARD:

/s/ JOHN H. REED Chairman.

$$ \frac{\text{OSCAR M. LAUKIL}}{\text{Member}} \quad 100\% $$

/s/ FRANCIS H. MCADAMS Member

/s/ LOUIS M. THAYER Member

/6/ TSABEL A. BURGESS Member

December 29, 1971

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Attachment

TRANSCIPTION OF CVR RECORD OF VOICE COMMUNICATION DETWEEN A TRANS WORLD AIRLINES BOEING 707 (FLIGHT TW31) AND AN AMERICAN AIRLINES BOEING 707 (FLIGHT AA 151) ON ARTIC CHANNEL 129.5 MIZ., FOLLOWING A NEAR MISS ON JUNE 11, 1971, NEAR PILIPSBURG, PENNSYLVANIA, (OAK 71-I-0052)

L.G.END

AA 151 Radio transmission made by the captain of American Airlines Flight 151.

TW 31 Radio transmission made by the captain of Trans World Airlines Flight 31

( ) Not clearly understood

SOURCE

CONTENT

AA 151 Cleveland Center, American one five one

TW 31 This is TW thirty-one, are you on the frequency?

AA 151 Roger, TWA thirty-one, American one fifty-one

TW 31 Ok, did you, ah, did you see us, ah, by Philpsburg there?

AA 15L Negative, we didn't see you at all

TW 31 Ch man ! Ah, we had to take evasive action to avoid colliding with you--were---I guess you went right over Philipsburg didn't you.

AA 151 No we didn't. We went to the south of it

TW 31 Yeah that's ah, you were at thirty five. You see us out to ah, your right. I think we're at three o'clock to you

AA 151 Okay, we have you over at the right

TW 31 Man, if we didn't see you, ah, we'd both be down there on the, ah, -- ah terrin down below. It was ah-- pretty hairy

AA 151 Oh, that's why I couldn't understand the heading that he gave us in the first place. He turned us to one nine zero on the heading

TW 31 Yeah, okay I'm ah, I am going to make a file a near miss and you do the same, if you will. I've had one midair collision and I don't like to have another one

AA 151 Okay, this is TWA thirty-one?

TW 31 Affirmative, and it happened at, ah, ah, at, ah, let's say, ah fourteen, ah, fourteen twenty eight and we were eleven miles at of Philipsburg at flight level three five zero

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Transcription (2)

SOURCE

CONTENT

AA 151 Correct

TW 31 Okay, where you guy going?

AA 151 We're going to St. Louis

TW 31 Where you based?

AA 151. Chicago

TW 31 Okay, ah, ah, I think it's the fault of the radar controllers down below and this shouldn't be. We're both transponder equipped and, ah, we've had too many midair collisions as it is

AA 151 Right

TW 31 And the (animal Hiber) says hello

AA 151 Way

TW 31 We're based in IA

AA 151 Okay

End of conversation