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service for a short period in 1985. Weather enroute [[en route]] can cause delivery delays. Flight turnaround ferry operations have experienced minor delays due to weather; however, other ferry operations have experienced rather significant delays. It is felt that this risk is always present, and it represents only a schedule risk rather than a safety of flight risk. It is difficult to quantify the program risk of ferry and turnaround operations. The risk is composed of increased handling, the SCA flight environment, and the single string nature of the operations. Additionally, nearly 20 percent of the useful ferry life of the SCA already has been flown. The operations risks are controlled by sound, conservative procedures. XVI. ORBITER TIRES The Orbiter tires are manufactured by B. F. Goodrich and are designed to support a nominal Space Shuttle landing up to 240 000 pounds at 225 knots with 20 knots of crosswind. They have successfully passed testing programs yet have shown excessive wear at KSC, especially when crosswinds are involved. The tires are rated as criticality 1. Hence, there are scenarios that could result in loss of control at very high speeds for loss of a single tire. The tires designed for the operational program are an upgrade to those tires used for the ALT program. Those original tires were required to support an Orbiter landing weight of up to 227 000 pounds with a touchdown velocity of 225 knots. Those tires carried a 28-ply rating. The current tires were upgraded to a 34-ply rating using 16 cords. The ALT tires were never tested for crosswind loads since that was not the accepted practice in the industry. Based upon ALT experience, crosswind testing was added to the Space Shuttle tire certification process. To date, Orbiters have landed with a maximum of 8 knots of crosswind at the KSC runway resulting in heavy tire wear, both as spinup wear and crosswind wear. The spinup wear increase was probably the result of a higher landing speed due to a moderate tail wind. Dynamometer tests have shown that these tires can survive conditions well above the design specification. Therein lies part of the problem. The dynamometer tests have not been able to accurately simulate the surface effects actually seen inflight. A Langley Research Center test track has been used to give a partial simulation of the KSC landing case. This test apparatus will be upgraded for further testing the summer of 1986 in an attempt to include all the representative flight loads and perturbing conditions. The tires have undergone an extensive set of testing to examine effects of vacuum exposure, temperature extremes, cuts, leakage tests, side force test, load tests, preroll/storage tests, and wheel roll life tests. The tires have been qualified in all these areas without trouble. -B25-
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Wasn't sure whether to mark the original page number. At the bottom middle -B25-
