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The Ministry of Education and Science of Russia Samara State Aerospace University (National Reserch University)

Examples of p erformance of lab oratory works on the sub ject "Reliability and Op eration of Airplanes"
Electronic Metho dic Instructions

SAMARA 2011


The development programme for 2009-2018 of Samara State Aerospace University named after Academician S. P. Korolyov (National Research University) Compiler and translator: Mrykin Sergey V. Mrykin, S. V. Examples of performance of laboratory works on the sub ject "Reliability and Operation of Airplanes". = " ". [Electronic resource]: Electronic Metho dic Instructions/ S. V. Mrykin; The Ministry of Education and Science of Russia, Samara State Aerospace University. Electronic text and graphic data (264KB). Samara, 2011. 1 CD-ROM. Examples are intended for tutors and used for training masters on the sub ject "Reliability and operation of airplanes". The examples is a part of postgraduate programmes which were developed based on using new educational technologies, resources and distance-learning systems for the Masters programme "Designing, construction and CALStechnologies in aircraft engineering" for educational direction 160100.68 "Aeronautical Engineering". Prepared by the Department of Aeronautical Engineering SSAU.

c Samara State Aerospace University, 2011


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Metho d of blo ck diagrams
The task on a source is given [1, variant 1].

1.1

Task formulation

1. For certain blo ck diagram (var. 1) and time of working cycle ( = 1 hour) find reliability function P (S ) and operating time to failure Tf (S ). Blo ck diagram: S // 1 // Failure rate for elemets: NN element 1 2 3 4 5 6 Failure rate 0,0 0,0 0,0 0,0 0,0 0,0 i (t), h- 4 5 6 7 8 9
1

// 2 // // 3

// 4 //

// 5

2. Write answers on following questions: · May operating time to failure for system is increased twice by changing failure rate for element number 1? Calculate reliability function. · Calculate reliability function for system if element number 1 is failure-free absolutly?

1.2

Performance
S = 1 + 2 3 + 4 + 5 .

1. Failure rate for system:

Substitute the set numerical values: S = 0, 04 + 1 в 0, 05 в 0, 06 + 0, 07 + 0, 08 = 0, 193 h-1 . 3


Failure function: P (S ) = 1 - S = 1 - 1 в 0, 193 = 0, 807 Operating time to failure: Tf (S ) = 1 1 = = 5, 18 h. S 0, 193

2. Second part task includes two questions. We'll to begun with second question. 2.2. In limit element number 1 failure-free absolutly, that is 1 = 0. Then: S = 1 в 0, 05 в 0, 06 + 0, 07 + 0, 08 = 0, 153 h-1 . Failure function: P (S ) = 1 - S = 1 - 1 в 0, 153 = 0, 847 Operating time to failure: Tf (S ) = 1 1 = = 6, 54 h. S 0, 153

2.1. Reliability function and operating time to failure have increased, but not twice, hence, to increase operating time to failure twice due to element number 1 it's impossible.

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2

Reliability analysis system
The task on a source is given [2, figure 4].

2.1
2. 1. 1

Studying system
Analysis and addition of initial data

Yaw control system is shown on (figure 1).

1 rudder p edal unit; 2 rod; 3 crank; 4 bracket; 5 trimming effect mechanism; 6 artificial spring feel unit; 7 b ooster; 8 autopilot steering machine.

Figure 1

Control channel of rudders

In yaw control system hinge brakets 4 25, bell cranks 3 17, control ro ds 2 16. Purpose system [3]: necessary efficiency of lateral control. Functional failures [3]: decrease efficiency; increase efficiency; self-turn one or both rudders; change control efforts; fluctuations one or both rudders. We receive type airplane FULCRUM. Flight mission: training flight by close route, flying figure "flank"on one of sites route. Expected conditions of operation: flight above deserted district in simple meteo conditions in afterno on. Flight altitude 5 km, length of route 600 km, time of flight = 1 hour. 5


2. 1. 2 N 1 1 2 3 4 5

Elements failures analysis Element name 2 Rudder pedal unit Control ro d Bell crank Bracket Trim effect mechanism в 106 , h 3 0,3 0,05 0,05 0,04 1,0
-1

6 7 8

Feel mechanism Bo oster Servo unit

0,5 5,0 3,0

Failure element 4 Jam in swivels Jam in swivel Jam in swivel Jam in swivel Move operating ro d DC motor in extreme position Jam in swivel Hydrofeed opening Circuit opening

Failure system 5 Increase efforts Increase efforts Increase efforts Increase efforts Increase efforts

Increase efforts Increase efforts Failure servo unit

At the failures analysis for elements control system following assumptions are received: 1. Wedging and disconnect in hinges, for the received system of maintenance and repair, event practically incredible. 2. Servo unit 8 is electrohydraulic mechanism, connecting to bell crank 3.7. At failure servo unit control system is blo cked. 3. Hydraulic actuator 7 (bo oster) has reversible connecting. 4. Increase control efforts is estimated by following criterion: [Pp ]l < Pp [Pp ]s , where Pp pilot efforts to pedals; [Pp ]l = 9, 0 daN long time maximal efforts to pedals; [Pp ]s = 70, 0 daN short time maximal efforts to pedals. 5. The effort to pedals cannot be removed simultaneous turning other control surfaces. 6. Yaw control has to go o d state for execute flight mission. For the received assumptions extreme limitations are upset, hence special situation can be classified as emergency. 6


2. 1. 3

Normative level for op erating time to failure

In accordance with [2, table 1] normative operating time to failure for emergency is: [Tf ] = 0, 3 · 107 h.

2.2

Block diagram

S

// 1 // 4.1­4.25 //

// 2.1­2.16 // 5 // 7

// 3.1­3.17 // // // 6 // //

// 8

// 3.18

Failure intensity for system: S = 1 + 162 + 173 + 254 + 5 + 6 + 7 3.18 + 8 = = 10-6 · (0, 3 + 16 · 0, 05 + 17 · 0, 05 + 25 · 0, 04 + 1, 0 + 0, 5+ +1, 0 · 5, 0 · 0, 05 · 10-6 + 3, 0) = 6, 45 · 10-6 , 1/h. Operating time to failure: Tf = 1 1 = S 6, 45 · 10
-6

= 0, 155 · 106 h.

2.3

Analysis result discussion
Tf (= 0, 0155 · 107 h) [Tf ](= 0, 3 · 107 h),

Reliability criterion:

is not executed, hence system redesign is needed. 1. Bell crank 3.7 construction is changed from supported to summarizing, then failure servo unit is not blo cked control system. Blo ck diagram will be shown: S // 1 // 4.1­4.25 // // 2.1­2.16 // 5 // 7 // // // 3.18 7 // 3.1­3.17 // // // 6


Failure intensity for system: S = 1 + 162 + 173 + 254 + 5 + 6 + 7 3.18 = = 10-6 · (0, 3 + 16 · 0, 05 + 17 · 0, 05 + 25 · 0, 04 + 1, 0 + 0, 5+ +1, 0 · 5, 0 · 0, 05 · 10-6 ) = 3, 45 · 10-6 , 1/h. Operating time to failure: Tf = 1 1 = S 3, 45 · 10
-6

= 0, 29 · 106 h.

2. Change trim effect mechanism such, that 5 = 0, 2 · 10-6 1/h, then S = 3, 15 · 10-6 1/h, and operating time to failure for yaw control system Tf = 0, 32 · 106 h, reliability criterion is executed.

Bibliography
[1] Vilchek, M.I. Reliability, fail-safe, operating. Metho d of blo ck diagrams and estimate reliability system [Text]: metho dic instructions/ compilers M. I. Vilchek. Kuibyshev: KuAI, preprint, 1981. 27 p. (in Russian). [2] Napadov, K.A. Reliability analysis airplane system at design [Text]: metho dic instructions. Samara: Publishing SSAU, 2010. 17 p. (in Russian). [3] Mrykin, S.V. Functional failure effects airplane systems [Text]: manual. Samara: Publishing SSAU, 2009. 49 p. (in Russian).

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