Viewing page 94 of 172

This transcription has been completed. Contact us with corrections.

way design criteria. In order to assess the end-of-mission runways at EAFB and KSC, some multiple failure scenarios and Flight Rules landing weather condition violations were developed into three scenarios. The results are summarized in table 5. It should be noted that all cases involve conditions that would not be allowed in flight due to Flight Rule placards. All scenarios assumed a heavy weight (240 000-pound) landing and a 40 MFP brake energy.

In the first failure scenario, a lateral departure case was defined which assumes two blown tires on the same side of the Orbiter and loss of the nosewheel steering. It was found that departure from the runway occurs at 120 knots for a 20-knot crosswind (10 knots over allowable) down to 40 knots (0 crosswind). At Flight Rule limits of 10 (nominal EOM) or 15 (TAL) knots crosswind, off runway scenarios may occur. The speed at which the Orbiter leaves the runway is reduced as crosswind values are changed. There is no departure if the crosswind comes from the side with the failed tire and is greater than 8 knots. With two blown tires, it is assumed that the wheel rims will fail and loads will be taken by the landing gear strut. The safest surface for this case is a concrete surface with a lateral stabilized shoulder (runway 22 at EAFB). The worst surface is the lakebed, since it is assumed the strut will dig in and probably fail structurally.

The second scenario examines longitudinal departure and is based on a hot day with a tailwind/crosswind failure plus tire or brake failure and no nosewheel steering. This case will result in an overrun for a 12 500-foot runway. Clearly, the runway with the best margin is the lakebed at EAFB, but the KSC and EAFB concrete runways are also good and comparable. The pacing runways for this case are the short TAL abort runways, such as DAKAR.

A third scenario examines a loss of 25 percent of the rolling friction at EAFB and DAKAR. This reduction would most likely result from moisture. Admittedly, this scenario is very unlikely since the weather forecasting probability is generally good at EAFB and forecast duration is short at DAKAR. The results can be a lateral or longitudinal departure. The KSC runway, designed as an all-weather runway, provides the safest stopping situations. It should be noted that the Orbiter tires are designed to dissipate heat and have a very thin tread which is prone to hydroplaning.

DAKAR is marginal for all landing conditions, KSC is good for runway surface problems, EAFB 22 is best for lateral departure cases, and all end-of-mission runways are acceptable for the longitudinal cases, with the lakebed runways providing the greatest margin.

XII. OFF RUNWAY RESCUE

In the event that the Orbiter landing results in an off runway situation, the convoy team is prepared to assist in the rescue of the crew. Operations take one of two forms, depending upon whether the crew requires assistance to egress the Orbiter or if their egress must be assisted by the ground team. 

-B19-