Designing the L-1011 to minimize rotor failures effects

Design philosophies used in the L-1011 aircraft to provide protection against rotor fragments include: (1) incorporating into the rotor design features that tend to promote small fragments if failure occurs; (2) containing the fragments within the engine shell or greatly reducing the energy content of those fragments that are eventually uncontained; (3) shielding vulnerable elements or systems with heavy structural members that tend to stop or deflect high velocity fragments; and (4) incorporating redundant and/or backup systems into the basic design and separating these systems so as to minimize the probability that more than one system will be damaged by an uncontained rotor fragment. Some of the design features that were incorporated into the Rolls-Royce RB211 engine are discussed, and two in-service experiences are considered in order to illustrate the practical operation of these features

NACA Technical Notes

From Summary: "This paper deals with the single problem if circular shell-supported frames subjected to concentrated loadings. A mathematical attack is developed and presented in the form of nondimensional-coefficient curves.

Analysis of a Thin Elastic Ring Under Ar-bitrary Loading

] 3 are to be congratulated for their presentation and formulation of an excellent procedure for determining external displacements and internal loads in a thin elastic ring subjected to any self-equilibrating load system. The advantage of proceeding from displacement to load analysis (as was done in [1]), rather than vice versa, is certainly recognized. The authors of this discussion are particularly interested and gratified since the authors of [1] used one of the discussion authors' papers [2] among their references in extending the work to solve a class of external loadings not included in [2]. Furthermore, it is always welcome and fortifying to observe others who take another approach to selected problems and obtain the same correct results, as was demonstrated in [1] in applying the approach to some of the cases included in [2]. The mathematical equations in this paper are closed form expressions, a situation which could not be permitted in [2] since it was required in that procedure to assign absolute values to the angular arguments. The series expressions seem to eliminate some of the concern for sign and, possibly, magiiitude difficulties with regard to the internal load calculations. However, it is deemed necessary, even in this paper, to exercise a degree of caution particularly in applications to rings subjected to multiload sets and distributed loads acting over more than 90-deg arcs. It is noted that Liu and Chiu seemingly saw a need for this caution, as evidenced by their sign convention in Recently, it was brought to the attention of the discussion authors (by [3] 1 Liu, J. Y., and Chiu, Y. P., "Analysis of a Thin Elastic Ring Under Arbitrary Loading," presented at the Winter Annual Meeting, Detroit, Mich., Nov. 11-15,1973, ASME Paper No. 73-WA/DE-6. 2 Kurajian, G. M., and Na, T. Y., "Thin Elastic Rings Subjected to Ra-.dial Load Sets," JOURNAL OF ENGINEERING FOR INDUSTRY, TRANS. ASME, Series B, Vol. 94, No. 3, Aug. .1972, pp. 783-788. 3 Williams, H. E., Applied Mechanics Reviews, Vol. 26. No. 8, Aug. 1973, p. 947. 4 Wignot, J. E., Combs, H., and Ensrud, A. F., "Analysis of Circular Shell-Supported Frames," NACA TN-929,1944. 5 Prescott, J., Applied Elasticity, First Ed., Dover Publications, New York, 1961 6 Roark, R. J., Formulas for Stress and Strain, Fourth Ed., McGrawHill, New York, 1965. Authors' Closure The authors agree with the comments made by the discussers that in solving thin ring problems one must be very careful about' the sign convention used in the mathematical derivations in order to obtain correct solutions. This is especially so when the loading condition is complex. In the authors' paper the sign convention for the ring displacements as well as the applied loads is described in Though closed-form solutions have been presented for the several cases discussed by the authors, it is noted that when a distributed load function is complex, numerical integration by a digital computer may become necessary