Operation Linebacker, the code name for the new interdiction campaign, would have four objectives: to isolate North Vietnam from its sources of supply by destroying railroad bridges and rolling stock in and around Hanoi and north-eastwards toward the Chinese frontier; the targeting of primary storage areas and marshalling yards; to destroy storage and transshipment points and to eliminate (or at least damage) the North's air defense system. With nearly 85 percent of North Vietnam's imports (which arrived by sea) blocked by Pocket Money, the administration and the Pentagon believed that this would cut its final lines of communication with its socialist allies. China alone shipped an average of 22,000 tons of supplies a month over two rail lines and eight major roads that linked it with North Vietnam.
On 10 May Operation Linebacker began with mass bombing operations against North Vietnam by tactical fighter aircraft of the Seventh Air Force and Task Force 77. Their targets included the railroad switching yards at Yên Viên and the Paul Doumer Bridge, on the northern outskirts of Hanoi. A total of 414 sorties were flown on the first day of the operation, 120 by the Air Force and 294 by the Navy and they encountered the heaviest single day of air-to-air combat during the Vietnam War, with 11 VPAF MiGs (four MiG-21s and seven MiG-17s) and two Air Force F-4s shot down. Anti-aircraft artillery and over 100 surface-to-air missile firings also brought down two U.S. Navy aircraft (one of which was flown by aces Duke Cunningham and William P. Driscoll).
By the end of the month, American aircraft had destroyed 13 bridges along the rail lines running from Hanoi to the Chinese border. Another four were destroyed between the capital and Haiphong, including the notorious Thanh Hóa Bridge. Several more bridges were brought down along the rail line leading to the south toward the DMZ. Targets were then switched to petroleum and oil storage and transportation networks and North Vietnamese airfields. There was an immediate impact on the battlefield in South Vietnam. Shelling by PAVN artillery dropped off by one-half between 9 May and 1 June. This slowdown was not due to an immediate shortage of artillery shells but rather to a desire to conserve ammunition. U.S. intelligence analysts believed that PAVN had enough stockpiled supplies to sustain their campaigns throughout the autumn.
The intensity of the bombing campaign was reflected by the sharp increase in the number of strike and support sorties flown in Southeast Asia as a whole: from 4,237 for all services, including the RVNAF, during the month preceding the invasion, to 27,745 flown in support of ARVN forces from the beginning of April to the end of June (20,506 of them flown by the Air Force). B-52s provided an additional 1,000 sorties during the same period. The North was feeling the pressure, admitting in the official PAVN history that "between May and June only 30 percent of supplies called for in our plan actually reached the front-line units." In total, 41,653 Linebacker missions dropped 155,548 tons of bombs.
In addition to interdicting the road and rail system of North Vietnam, Linebacker also systematically attacked its air defense system. The VPAF, with approximately 200 interceptors, strongly contested these attacks throughout the campaign. Navy pilots, employing a mutually supporting "loose deuce" tactical formation and many with TOPGUN training, enjoyed a kill ratio of 6:1 in their favor in May and June, such that after that the VPAF rarely engaged them thereafter. In contrast, the Air Force experienced a 1:1 kill ratio through the first two months of the campaign, as seven of its eventual 24 Linebacker air-to-air losses occurred without any corresponding VPAF loss in a twelve-day period between 24 June and 5 July. Air Force pilots were hampered by use of the outdated "fluid four" tactical formations (a four-plane, two element formation in which only the leader did the shooting and in which the outside wingmen were vulnerable) dictated by service doctrine. Also contributing to the parity was a lack of air combat training against dissimilar aircraft, a deficient early warning system, and ECM pod formations that mandated strict adherence to formation flying. During August the introduction of real-time early warning systems, increased aircrew combat experience and degraded VPAF ground control interception capabilities reversed the trend to a more favorable 4:1 kill ratio.
Linebacker saw several other "firsts". On the opening day of the operation, Navy Lieutenant Duke Cunningham and his radar intercept officer, Lieutenant (j.g.) William P. Driscoll became the first U.S. air aces of the Vietnam War when they shot down their fifth MiG. On 28 August, the Air Force gained its first ace when Captain Richard S. Ritchie downed his fifth enemy aircraft. Twelve days later, Captain Charles B. DeBellevue (who had been Ritchie's backseater during four of his five victories) downed two more MiGs, bringing his total to six. On 13 October another weapons officer, Captain Jeffrey S. Feinstein, was credited with his fifth MiG, making him the final Air Force ace
by Robert L. Sumwalt
It's no secret. When a flight crew's attention is diverted from the task of flying, the chance of error increases. Over the years there have been dozens of air carrier accidents that occurred when the crew diverted attention from the task at hand and became occupied with items totally unrelated to flying. Consequently, important things were missed. Things like setting the flaps prior to takeoff, or extending the landing gear before landing. Things like monitoring altitude on an instrument approach, or using engine anti-ice for takeoff during a blinding snow storm.
In 1981 the FAA enacted FAR 121.542 and FAR 135.100 to help curb the number of these accidents. Commonly known as the "sterile cockpit rule," these regulations specifically prohibit crew member performance of non-essential duties or activities while the aircraft is involved in taxi, takeoff, landing, and all other flight operations conducted below 10,000 feet MSL, except cruise flight. (Click here to go to FAR 121.542 and 135.100 .)
It's unrealistic to expect a crew to fly together for several days and never discuss anything except items related to flying the aircraft. In fact, experts have demonstrated that in order to be most effective, crews need to talk -- even if it is just merely "get to know you" sort of chat. The sterile cockpit rule is a good rule because it clearly defines when it is time to set aside non-essential activities and tend strictly to the task at hand -- that of safely operating the aircraft.
In spite of the existence of the sterile cockpit rule over the past decade, pilots have continued to have accidents and serious incidents that perhaps could have been prevented. For the most part, disobeying the rule is not intentional. It just happens. But as this review shows, the consequences of non-compliance can be very serious. Truly, the sterile cockpit needs to be cleaned up.
This reviewer used the ASRS database to find specific examples of problems related to non-compliance with the sterile cockpit rule. We carefully reviewed 63 reports that had been previously coded by analysts as having some relevance to the sterile cockpit rule. Here is a synopsis of the problems that we found that could be attributed to sterile cockpit violations:48% were altitude deviations
14% were course deviations
14% were runway transgressions
14% were general distractions with no specific adverse consequences
8% involved takeoffs or landings without clearance
2% involved near mid-air collisions due to inattention and distractions.
The way in which the sterile cockpit rule was broken in each report was tallied and analyzed. Some reports contained more than one culprit. Many of the reports contained acknowledgments like this:
Following are the four most common reasons for non-adherence to the sterile cockpit rule:
The most habitually cited offense was extraneous conversation between cockpit crew members. Cited one First Officer:
The Captain of an air carrier aircraft admits to conversation not pertinent to flying duties:
Five reports detailed extraneous conversation with jump seat riders. The ability to ride on an air carrier's jump seat is quite a valuable privilege, but it is important that the additional cockpit rider not be allowed to create distractions. A look at two of these reports:
And in the other ASRS submission:
The connotation "extraneous conversation" does not always have to imply just those persons on board the aircraft. Look at how extraneous chatter with air traffic controllers introduced problems for these crews. Air traffic controllers, take notice:
And in another incident:
Distractions from Flight Attendants
Distractions caused by flight attendants visiting the cockpit or calling on the interphone were noted in almost one quarter of the reports in our data set. This was our second highest source of deviation from the sterile cockpit rule.
In another incident, the crew was surprised when they lined up with the wrong runway -- and doubly surprised when they noticed they were in an unplanned formation with a jet landing on the same runway!
Non-Pertinent Radio Calls and PA Announcements
Several reports we examined indicate that problems arose when non-pertinent company radio calls and PA announcements were made below 10,000 feet. Remember, below 10,000 feet if it's not directly related to flight safety, it's in violation with the sterile cockpit rule.
While being vectored in a busy terminal area, the Captain in the following report called on the company radio frequency to notify maintenance about a minor cabin discrepancy. As the reporter soon discovered, his absence from the ATC frequency caused an overload with his First Officer. Several ATC radio calls were missed. The controller growled a little, they lost their landing sequence, and the pilot's pride was hurt. But a valuable lesson was also learned.
Nowhere does Webster's define "sight-seeing" as an activity that is essential to the safe operation of aircraft. When sight-seeing is conducted by flight crew members below 10,000 feet, not only is it potentially dangerous, but it is illegal, as well. Two reports demonstrated that a cockpit full of sight-seeing crew members is an ASRS report looking for a place to happen -- possibly even an accident.
In another incident report:
Recommendations and Considerations
The sterile cockpit rule was designed to help minimize many of the problems that we just annotated. Judging from these reports, a safer operation can be achieved by simply abiding by the rule's guidelines.
In the Beginning
A good time to establish the desire to maintain a sterile cockpit environment is before beginning a trip. In briefing cockpit and cabin crew members the captain can politely say, "I think the sterile cockpit rule is really important, so we'll adhere to it. Okay?"
Setting the Standards
During the preflight briefing the captain should also inform the flight attendants how they can determine if the flight is above or below 10,000 feet. Many companies have already established procedures for this, such as a "10,000 foot PA announcement," or a call to the flight attendants on the interphone. However, these procedures require one crew member to be "out of the loop." And as evidenced by literally thousands of ASRS reports, the potential for problems (such as misunderstood clearances and altitude deviations) increases when a crew member is out of the loop. Some airlines have installed a cockpit-controlled "sterile cockpit light" that can be illuminated when descending below 10,000 feet and extinguished when climbing above 10,000 feet. For those who develop company procedures, consideration should be given to developing something that doesn't create its own set of distractions. With the increased use of two-crew member cockpits this consideration is increasingly important.
Unexpected calls or cockpit entry by flight attendants during the sterile cockpit period can be distracting and potentially dangerous. It is recommended that the Captain, during the pre-departure crew briefing, emphasize the importance of the sterile cockpit rule and request that flight attendant calls or entry during this time be undertaken only for reasons of great urgency. As one reporter resolves:
High Altitude Airports
Another reporter offered a good suggestion involving high elevation airports, where 10,000 feet MSL for the sterile cockpit boundary may be too low.
Low Altitude Flight
This reporter, a commuter pilot who often has cruise altitudes below 10,000 feet MSL, offers a similar worthwhile suggestion following an altitude deviation.
"I believe this situation occurred because our cruise altitude was 8000 feet, and we were accustomed to conversation and other activities along the route and were not observing the 'sterile cockpit' environment. Would suggest that, in these flight circumstances where cruise altitude is less than 10,000 feet, crews make a specific DME mileage their beginning for 'total concentration-sterile cockpit' procedures." (ACN 173707)
No person about to undergo major surgery would think too kindly of the surgical team who failed to sterilize themselves and their operating instruments before the operation. After a series of air carrier accidents and serious incidents, the traveling public feels the same way about their crew members. Keep the sterile cockpit "clean." Your fellow crew members and passengers are hoping that you will.