Air Safety

Refuelling Site

Therefore, the planners decided it was necessary to find a refuelling site which was in a remote area within unrefuelled range of the helicopter force, yet close enough to Tehran to allow the helicopters to carry the rescue force and their equipment to their destination with sufficient fuel reserves to support a subsequent rescue mission. These boundaries on the problem forced the planners to focus on a relatively constrained geographical area about 100 miles in diameter at some distance southeast of Tehran.

The site eventually selected was the only one which satisfied the demanding criteria, in that it was level, firm, and large enough for C;130 take-offs and landing and refuelling, met the requirement for tooth isolation and proximity, and provided usable visual references for night landing without use of aircraft lights. There was an obvious calculated risk in using the site because the area selected, code named Desert One, straddled a narrow, unpaved road. However, no other location could be found which would meet landing criteria and this risk was considered acceptable because of the calculated probability of very light night-time traffic on the road. For extra insurance, however, the concept of operations was adjusted to send in an advance C-130 with a combat control team abroad and a road security force to secure and organise the landing and refuelling area.

The planning for the operation underwent an almost continuous evolution since the quiet gathering of flight crews and helicopters began the day prior to Thanksgiving, 1979. One early decision was the selection of the US Navy RH-53D helicopter as the mission aircraft, based on its range, payload, and the fact that its familiarity as a fleet aircraft would help conceal the true reason for its presence in Iran’s nearby waters. (The Navy had procured 30 of these aircraft in the early 1970s and employed them routinely in an aerial mine countermeasures role). Six of these helicopters were transported to the aircraft carrier Kitty Hawk in the Arabian Sea in late November. These were later transferred to the Nimitz when she arrived in late January, carrying two additional RH-53s, to replace Kitty Hawk.

Meanwhile, the process of training; refinement of concepts and procedures, and more training was carried out in the final weeks of 1979 and into 1980. The bulk of the helicopter training was conducted secretly in areas of the Western United States where weather and topography approximate that of south and central Iran. The training aircraft were a mix of two similar models of the same basic design: three RH-53s and five CH-53s. (Although there are some differences in cockpit layouts between the two aircraft, the flight characteristics are virtually identical and crews were given extensive experience in the mission type – the RH model – throughout the training phase. In no respect was the fact that slightly different models were sometimes used during training considered an operational limitation by any of the planners or flight crews, either before or after the actual mission.)

The pilots selected were the best and the crew composition was specially adjusted for this mission. For comparison, the normal cockpit crew consists of an experienced pilot (the helicopter commander) and a less experienced co-pilot. For this mission, both pilots of each crew were highly experienced commanders to ensure the highest level of flying skills obtainable under the very difficult flying conditions contemplated. In view of the flight conditions actually encountered during the night of 24-25 April, this experience paid off.

The helicopter and flight crews were provided with the latest state-of-the-art electronic (Omega and inertial navigation systems) and visual navigational equipment available and adaptable to the RH-53D, including night vision devices. Even with these aids, the mission – and therefore the training – called for superior airmanship. Every effort was made to duplicate as closely as possible in training the distances, conditions, and stresses that the crew might have expected to encounter on an actual mission. This included some experience in flight through conditions of reduced visibility such as fog, and no moonlight, as well as refuelling and other ground operations at night in the desert with engines running on all helicopters.

Scenario Rehearsals

During the period between the preliminary planning efforts and the final mission execution, four full-scale scenario rehearsals with all elements of the force and about 20 exercises of separate parts of the planned mission were conducted. As the proficiency of the elements in the rescue force increased, intelligence improved and planning factors were validated, and as lessons continued to be learned from this intensive program, confidence gradually grew.

The entire organisation, the planners, and the Joint Chiefs of Staff became increasingly confident that the mission was not only possible but, in fact, had a good chance of success. From the beginning, the military planning, resource requirements, and force recommendations were fully supported. The size and composition of the planned rescue force were judged to be proper.

The Joint Chiefs of Staff made a final review of the entire plan, the training, and intelligence. They approved the plan, stated it was militarily feasible, and recommended that it be implemented. The many risks and uncertainties were clearly understood and taken into account, but by the time the countdown for the mission began in mid-April, the crews, aircraft (C-130s and helicopters), and rescue force were ready and there was an air of confident resolve among all participants.

April 24 was established as the planning date for beginning the mission. Selection of a date was necessary to begin deployment of the forces which had to be done by clandestine means for security reasons, but April 24 was not a firm and fixed date. Weather, intelligence and a host of other factors had to be considered for the final decision. The date could have slipped several days while waiting for suitable conditions, although a major extension would have jeopardised security. In early April, the President authorised an increased level of preparation for a possible rescue attempt. The necessary supporting deployments were blended in with other routine operations and crews and aircraft were “peaked” for mission tasking on short notice.

Six helicopters were initially put on board a carrier in late November 1979. At that time, six were considered sufficient for the entire mission as initially planned, with adequate backup for unforeseen maintenance problems. As mission planning was refined and more intelligence was gathered, the size of the rescue force was increased slightly. Two additional helicopters were added, both to accommodate the increased load and reduced helicopter performance as temperatures increased, and to provide an additional margin of confidence that the required number would be available if the plan were executed.

Increased Flying

Earlier, there had been a widespread reluctance to fly the shipborne mission aircraft often to avoid drawing excessive attention to their presence. By the end of January, the tempo of flying increased significantly, partly to establish a familiar pattern for observers, but more importantly, to permit regular exercising of helicopter systems and subsystems.

The helicopters had been maintained at a high level of readiness for a prolonged period of time and a special clandestine procedure had been established within the naval aviation supply system to keep the Nimitz supplied with essential helicopter parts in a timely fashion without revealing the true purpose. The helicopter detachment aboard the Nimitz had all the people and technical skills the on-scene commanders determined they needed. The maintenance officer used an extensive checklist to inspect all components of the aircraft. Components were replaced if they showed evidence of wear. Some parts were changed if they were approaching the last 20 per cent of their normal flying hour interval for change.

RH-53

When the decision was made to begin the countdown for the rescue mission, seven of the eight helicopters aboard the Nimitz were mission-capable. The plan called for a minimum of seven operational helicopters to depart the carrier and six operational helicopters to depart the desert refuelling site. Extraordinary efforts were made to expedite the necessary parts to bring the eighth helicopter into a full mission readiness status prior to the time the mission launched to gain even more confidence. This eighth helicopter was one that made it all the way to the refuelling site and would have flown on had the mission continued beyond the refuelling site.

The helicopter crews (pilots and crew mechanics) arrived on the Nimitz four days prior to the target date for the mission. In the period between arrival and mission execution, each of the flight crews flew its assigned mission helicopter on a thorough check-out of all systems. By the time the mission was ready to launch, crews were totally satisfied that they had not only the best helicopters available, but also the best maintenance and the highest prospects for success at any point in their training.

There were three separate pre-mission events that bear comment. First, a conscious decision was made to remove the sand screens (engine air particle separators, or EAPS) normally carried over the engine inlets. These screens were designed to protect the service life of the engines but carried a penalty in terms of weight, drag, and power loss. Since the aircraft were to be operating at very heavy gross weights and would have been abandoned once the mission was successfully completed, long-term engine life was not a consideration and the sand screens were removed to gain the maximum available engine performance. Removal of the sand screens had no known adverse impact on the mechanical performance of any of the helicopters.

Second, on the morning of mission execution, five of the eight mission helicopters were inadvertently wetted to varying degrees with salt water and foam spray from the hangar deck fire protection system. Within minutes, fresh water rinsing of the helicopters had begun and careful inspection of the possible impact was made by maintenance and crew people. No foam or salt water was found in any cockpit, communications or navigation equipment bay, or equipment compartment.

External electrical power was applied to each helicopter and all electrical systems checked out satisfactorily. As an additional precaution, the helicopters were brought up to the flight deck somewhat earlier than planned and the crews made extensive checks of engines, flight controls, and other systems prior to launch. No discrepancies were noted and it was the judgement of the pilots, crews, and maintenance people that the short duration, limited wetting, and the speed and thoroughness of cleanup had prevented any possible adverse impact on the mission. None of the material failures during the mission are attributable to the wetting.

Third is weather Early in November 1979, a select weather group was formed. This group, including the designated mission forecaster, began a series of climatological surveys and all of the necessary resources of the Air Weather Service were available and utilised extensively. The forecaster began early on to develop forecasts for flight routes planned in Iran for the mission as if they were to be flown that day. On a regular basis, he briefed the Joint Task Force commander and the commander made judgements on whether the weather was suitable for the mission. Often it was not.

The next day, actual, recorded weather conditions in Iran were compared with forecasted conditions, both to check the validity of the forecast and also to learn as much as possible about environmental factors affecting weather in Iran. Experience grew, and by late February there was high confidence in the weather forecasting for the routes.

On April 24, the forecaster forecast good weather for the helicopter flight route. The forecast called for nearly clear sky conditions, with high scattered overcast, good visibility, and favourable winds. The forecast was correlated with data from numerical models provided by the Air Weather Service, and it was concluded that the weather was satisfactory for the mission to commence.

Suspended Dust

As described later, the helicopter pilots encountered a series of unforecasted areas of suspended dust about halfway to the refuelling site. The Air Weather Service conducted an extensive post-mission analysis. The analysis concludes that all actual weather conditions occurred as forecast, with the exception of the dust phenomenon. There is nothing in any of the weather data to indicate that the dust was forecastable or, for that matter, any environmental conditions that could have caused it. There is a remote possibility, however, unlikely, that a downwash of air from thunderstorms about 50 miles to the west of the planned route could have stirred up the dust.

These thunderstorms were forecast accurately but were and are not now considered to be a likely factor. The Air Weather Service concludes that the dust was a very localised phenomenon. The state of the art does not enable forecasting such as spatial and temporal occurrence with any degree of reliability. Unpredictable and difficult flight conditions were ahead of the helicopter pilots as they prepared to take off from the carrier.

Take-off and en-route: Shortly after 7:30 pm local time in Iran on April 24, all eight helicopters departed the Nimitz fully mission-ready. Remarkably, some five and a half months after planning had begun, the mission was launched with the veil of total secrecy still in place. The carrier task force had taken deceptive action to prevent any observers in the area from being alerted at the last minute to unusual activity. (The C-130s carrying their fuel, the refuelling site security force, and the rest of the rescue force were already en route to Desert One).

The helicopters flew in en route formation, four sections of two each in roughly a diamond pattern. Using the night vision devices, each crew was able to maintain visual contact with all other aircraft as they proceeded toward the coast at low altitude. They crossed the coastline 100ft above the ground, on course, away from populated areas with winds and weather as predicted. Except for an intermediate gearbox chip light experienced by No. 8 (which was not considered a serious discrepancy), the flight continued uneventfully through the first third of the distance.

At this point, No. 6 helicopter received a cockpit warning light indicating possible imminent main rotor blade failure, an unusual but potentially disastrous occurrence. The crew elected to land immediately to confirm the malfunction and dropped out of the formation toward a lake bed below. In accordance with preplanned radio silence procedures, the last aircraft in the formation, No. 8, followed No. 6 down to render assistance and, if necessary, evacuate the crew.

Upon landing, the crew of No. 6 visually inspected a mechanical indicator located on each of the rotor blades. This inspection confirmed that one of the blades had actually experienced a loss of blade spar pressure indicating the possibility of an incipient blade failure. The aircraft commander made an abort decision and the crew boarded helicopter No. 8 after transferring all classified documents and equipment. No. 8 helicopter took off and continued the mission. At this point, there were still seven operational helicopters en route, one more than the mission required beyond Desert One.

Dust Clouds

Several miles ahead, the rest of the formation was approaching what at first appeared to be a fog bank, but which turned out to be the first of several nearly continuous areas of suspended dust. Immediately upon penetrating the dust, visibility was degraded to the point where it was impossible for all mission aircraft to maintain visual contact with one another. The aircraft separated into one and two aircraft flights and they continued on course. Ground references were obscured or completely invisible and the inherent vertigo-inducing properties of the night vision devices were compounded.

This weather phenomenon had not been forecast and the degree and duration of obscured visibility thoroughly tested the crews’ previous training experience with reduced visual contact. Although unsure of the nature or extent of the phenomenon they were experiencing, and wishing not to communicate in a radio-silence environment, the crews elected to proceed.

In their judgement, flight conditions did not warrant a radio call to recommend mission termination. (Some of the crews tried to maintain visual formation on one or more of their colleagues. However, the combination of reduced visibility – likened to being “inside a bowl of dark milk” – and frequent vertigo made it difficult to maintain formation integrity.)

The first flight leader (helicopter No. 1) and his wingman had proceeded into the first cloud for a while, expecting to break out into the clear momentarily. When conditions did not improve, the leader elected to reverse course and exit the cloud. No. 2 followed him out and both landed.

The leader anticipated that the rest of the formation would observe his turn and likewise pull out and land until the cloud (or storm – no one was sure what they were in) “blew past”. Based on no radio calls from other helicopters, he concluded that all were proceeding on the mission and after about 20 minutes he continued his flight. He and No. 2 took off again, reentered the dust cloud, and continued to navigate along the planned course under instrument flight conditions. By this time, they were at the tail end of the formation.

Shortly afterwards, the second major material problem in the helicopter formation occurred. The No. 5 helicopter had cleared the first areas of dust like the others and entered another. For a time the crew attempted to remain in visual contact with aircraft 3 and 4 which were ahead of them. Seeing the serious control problems they were having and experiencing the same problems themselves due to vertigo, the crew of No. 5 soon became visually separated from the rest.

About 45 minutes into this second area of dust, No. 5 experienced a malfunction of a motor that powered a blower providing cooling air to an aircraft power supply. The power supply overheated and failed, rendering the aircraft’s heading reference inoperative. Additionally, other flight instruments and part of the flight control system that were served by this power supply either failed or began to operate intermittently.

An already difficult navigation problem was becoming impossible. At one point, the crew descended on their radar altimeter to about 75ft above the ground and still could not see the surface, either for navigational reference or for a possible landing until flight conditions improved. The crew concluded that the navigation references available to them, both from onboard equipment and visually, were insufficient to maintain the course.

They knew that this situation would soon become extremely dangerous. While they were at that time still over reasonably level terrain, they were aware that they were less than half an hour away from a range of mountains standing between them and the refuelling point.

They were faced with some difficult choices. There appeared to be no way to navigate the valleys ahead safely and they were not sure they could climb above the mountains. Even if they could do so, they were reluctant to attempt it because of the risk of exposing their aircraft to possible detection and premature discovery of the mission. Moreover, each mile they continued on course took them farther from the Nimitz, the only possible safe recovery site. (At that, they were doubtful whether they had enough fuel to permit them to recover on Nimitz.)

Faced with the risks of attempting to penetrate the mountains ahead, they reluctantly aborted, reversed course, found their way out of the dust, and subsequently recovered aboard Nimitz with only minutes of fuel remaining. Although no one knew it yet, the failure of their navigation instruments and their subsequent abort would foreclose continuing the mission because of a third unpredictable and abnormal material failure, this one on helicopter No. 2.

Failed System

About two hours after take-off, the crew on No. 2 received a cockpit indication of a failed second-stage hydraulic system. (They would later discover that a crack had occurred in a jam nut located outside of the crew and cargo compartments, causing all hydraulic fluid in the second stage system to be pumped overboard. Since the pump is cooled by its own hydraulic fluid, the dry pump soon burns out.) This is a potentially dangerous malfunction in the RH-53, particularly under conditions of heavy loading.

If the first stage were also to fail, or if the demands of the first stage were to exceed its capability with a failed second stage, the flight controls would lock and a crash would be likely. Despite this continuous risk, along with the difficulties of navigation and visibility being experienced by everyone, the crew of No. 2 stuck with the mission. They landed safely at Desert One, still hoping there might be some way to C-130 repair a malfunction whose seriousness they had not yet been able to verify in flight.

C-130

Because of the delays, irregular flight paths flown and reduced airspeed to enable navigation, the first aircraft arrived about 50 minutes behind schedule, and the last about one hour and 25 minutes late. Their order of arrival was 3, 4, 7, 8, 1 and 2. No. 8 landed about 15 minutes before 1 and 2 which came in together. As they arrived, each proceeded to commence refuelling. All had emerged from the dust 30 to 40 miles prior to reaching Desert One and they had been thoroughly taxed by the ordeal they had just been through. Nevertheless, they began preparations immediately for the next phase of the mission.

At Desert One: The C-130s had been on the ground (with engines left running, as planned, to avoid the problem of a failed starter) for about two hours before the first helicopter arrived. Within a very few minutes after the first C-130 had landed with the combat control team aboard, an Iranian bus carrying 40-plus civilians drove into the planned refuelling area along the unpaved road.

In accordance with planning developed in the event of traffic on the road, the bus was stopped and the passengers were detained (courteously, and without harm to any of them) outside the actual area of refuelling operations. A few moments later, a fuel truck and a following light truck approached. When the truck was stopped, the driver ran to the following vehicle and fled the area. The occupants of the fuel truck and the following truck never got close enough to the C-130s to see what was going on. The judgement was that the mission had not been compromised. The C-130s were on the ground for a total of over four hours and these three vehicles were the only traffic along the road.

Helicopter Arrival Awaited

With the landing and refuelling areas secure, the C-130s and their accompanying rescue force positioned themselves to await the arrival of helicopters.

Since the order of the formation changed in the dust cloud, the flight leader landed next to last. As soon as he had positioned himself and begun refuelling operations, he began to assess the status of the other aircraft in the helicopter flight. He confirmed that No. 6 had aborted, although at this point he had no way of knowing that No. 5 had also turned back. While the refuelling was underway, the rescue force began to load aboard the helicopters for the onward flight to their forward location. Since six aircraft had landed, the minimum number required to complete the mission, the initial presumption was that the mission would continue as scheduled. The rescue force commander had gone aboard the helicopter flight leader’s aircraft to verify the status of the mission and was awaiting confirmation.

Meanwhile, the crew of helicopter No. 2, positioned to begin taking on fuel from their C-130, had for the first time been able to visually assess the extent of the hydraulic problem. They visually verified that a crack had occurred topside, causing the loss of the secondary system’s hydraulic fluid and the failure of the second-stage hydraulic pump. It was impossible to repair this malfunction at the refuelling site. Even if a spare pump had been available, there would not have been sufficient time to repair the source of the leak, replace and service the pump and still get to the forward location before daylight.

The co-pilot of the No. 2 helicopter moved to the flight leader’s helicopter to report on the condition of his aircraft. Despite the disappointing implications of the decision, the helicopter force leader confirmed that this was an aircraft abort item and that he therefore had only five operational helicopters left at his command.

This fact was discussed among the onsite commander, the rescue force commander, and the helicopter force commander and they revalidated the earlier planning agreement that the mission could not continue with fewer than six operational helicopters. After agreement on this point, they communicated by radio their status to the Joint Task Force Commander, who in turn relayed to Washington by secure radio the situation and the recommendation to abort. The President concurred in the decision that the mission could not continue and preparations for withdrawal were begun.

Under this circumstance, the plan called for the operational helicopters which had been refuelled to return to the Nimitz. After they took off, the C-130s with the ground rescue force were to return to their departure base. If possible, the partially disabled helicopter (No. 2) would be moved away from the refuelling area and destroyed. The bus passengers would be released unharmed.

It was at this point that chance once again intervened in the mission, this time with tragic results. Since the formation breakup made it impossible to be certain how many helicopters would finally reach the refuelling site until, in fact, they stopped arriving, each helicopter had taken a directed refuelling position on one of the C-130s.

In accordance with the plan, all C-130s and all helicopters were refuelling with their engines running, except for the aborted No. 2 which had terminated refuelling and shut down its engines for the time being. Three helicopters (3, 4, and 8) had refuelled from the northernmost of the three refuelling C-130s, No. 1 helicopter from the middle C-130, and No. 2 (initially) and 7 from the C-130 on the south side of the road. All the operational helicopters had enough fuel to continue the mission or to return to the Nimitz except for No. 4, which needed more to top off his tanks for the return flight to the Nimitz. His assigned C-130 could not give him any more without cutting into his own fuel reserve and endangering his recovery.

Therefore, the decision was made to reposition No. 4 to the other C-130 north of the road (which had extra fuel since only one of his assigned helicopters had arrived). In order to provide room for No. 4 to move, however, one of the flanking helicopters had to reposition. No. 3 was directed to clear and, as he applied to lift, he produced a cloud of dust. He was observed to lift off slightly, begin to move to the left, and then begin to drift back to the right. As the helicopter passed over the left wing of the C-130, it banked about 20 degrees to the right and its rotor blade struck the C-130. The fire broke out immediately and both aircraft were quickly engulfed in flames.

The C-130 was heavily loaded with people and munitions. Accessible personnel in both aircraft were evacuated in a quick and orderly display of professional discipline, without which the death toll could have been far higher. Unfortunately, five Air Force crew members perished in the cockpit of the C-130 and three Marines perished in the rear of the helicopter. Both helicopter pilots and several aboard the C-130 were burned to varying degrees.

The fire was too large to be extinguished and was far too intense to continue attempts to recover the bodies of the trapped crew members. Moreover, munitions began to cook off in the heat and fragments began striking helicopters – not only those in the immediate vicinity of the burning C-130 but those in other positions as well.

After the collision, helicopter crews aboard No. 4 and No. 8 immediately shut down their engines and evacuated their aircraft. No. 1 aircraft nearby also shut down after being struck by a fragment that split an in- ternal fuel cell.

South of the road (about 250 yards from the accident), No. 2 had already shut down and No. 7 requested instructions and received a command over the radio to shut down and load aboard a C-130. (It had earlier been decided that if, for some reason, the helicopters could not depart the area and evidence of their presence would clearly remain behind, the crews were to evacuate the area aboard the C-130.)

Critical Factors

Time and fuel were becoming critical factors. A great deal of fuel had been consumed and transferred. The C-130 aircraft, which had been sitting on the ground for a matter of hours with engines running, were getting low on fuel for the return leg, especially since they would now have to return with a heavier load than originally planned.

The on-scene commander decided not to destroy the helicopters. In his judgment, explosive destruction would make an already dangerous situation unmanageable. It would have greatly jeopardised the C-130s and could have caused the loss of many more lives. Likewise, retrieval of classified material aboard the helicopters was determined to be too dangerous, both for the helicopter crews themselves (especially those whose helicopters were close to the flaming wreckage) and potentially for the recovery of the entire force if more time was lost.

There was no possibility of recovering the bodies of eight men who had perished. The heat was too intense and the fire would burn for hours. All troops and crew members were ordered aboard the remaining C-130s immediately. They boarded in a rapid but orderly fashion after a thorough last check for people and the aircraft departed with on-scene medical personnel caring for the wounded.

The take-offs of the overburdened C-130s across this desert track provided another final exceptional feat of airmanship in a mission marked by tragedy as well as incredible courage.