Bend Allowance Formula Quiz for Aviation Maintenance

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Questions and Answers

What is the maximum allowed wrinkle or kink in tubes for fluid systems with working pressures of 500 psi or greater?

1% of the tube OD (correct)

0.5% of the tube OD

5% of the tube OD

2% of the tube OD

Why is it essential to determine the cause of a tube failure?

To report the incident to the authorities

To identify the manufacturer's defect

To replace the tubing with a new one

To prevent similar failures from occurring in the future (correct)

What is the purpose of pressure-testing tubing prior to installation?

To ensure the tubing can withstand several times the normal operating pressure (correct)

To test the tubing's flexibility

To ensure the tubing can withstand normal operating pressure

To test the tubing's durability

What should be used at points where the tubing passes through bulkheads?

Flexible grommets or hose Signup and view all the answers

What is the minimum clearance required between tubing and structure or rigid members, unless otherwise specified?

1/16 in. Signup and view all the answers

What is the primary reason for replacing damaged aircraft fluid lines?

To ensure safe operation of the aircraft Signup and view all the answers

Why may replacement tubing need to be fabricated?

Because replacement parts are not available Signup and view all the answers

What is the maximum allowable distance between supports for tubing, according to the table?

Specified in the table, but not provided in the text Signup and view all the answers

What is the purpose of using the Bend Allowance Chart?

To calculate the bend allowance Signup and view all the answers

What is the formula for calculating bend allowance?

2πR / 360° Signup and view all the answers

How do you calculate the flat dimension?

Subtract the setback for each bend from the overall dimension Signup and view all the answers

What is the purpose of dividing the bent object into flats and bend allowances?

To calculate the overall length of the bent object Signup and view all the answers

What is the minimum bend radius for tube bending?

2.5 to 3 times the OD Signup and view all the answers

What is the acceptable method for bending soft, non-heat-treated aluminium tubing in an emergency?

Bending by hand to form the desired radius Signup and view all the answers

What is the objective of tube bending?

To obtain a smooth bend without flattening Signup and view all the answers

What is the purpose of the stick diagram of tubing development?

To demonstrate the layout of the calculations Signup and view all the answers

What is the primary concern when cutting tubing?

Producing a square end, free of burrs Signup and view all the answers

What tool is used to remove both inside and outside burrs from tubing?

De-burring tool Signup and view all the answers

What is the consequence of slight damage to the tubing wall during deburring?

Fractured flares or defective flares may occur Signup and view all the answers

Why should the cut end of the tube be polished before flaring?

To remove any sharp edges that could cause the tubing to crack Signup and view all the answers

What are the two major types of tube joints?

Flared and flareless fittings Signup and view all the answers

What is the purpose of the tube flaring tool?

To prepare tube ends for flaring Signup and view all the answers

What can happen to the tube if it is not properly cleaned and deburred?

Draw marks can spread and split the tube when it is flared Signup and view all the answers

What should be checked on the tube ends before flaring?

The roundness, square cut, and cleanliness of the tube end, and the absence of draw marks or scratches Signup and view all the answers

What is the purpose of the swivel nut or flange?

To secure the nipple to the mating connection in the fluid system Signup and view all the answers

What is unique to each manufacturer's hose fittings?

The characteristics and tolerances Signup and view all the answers

Why should nipples and sockets from different manufacturers not be intermixed?

Due to differences in characteristics and tolerances Signup and view all the answers

What is the purpose of colour-coding on hose fittings and nuts?

To show the material used Signup and view all the answers

What is the recommended pressure for testing fabricated hoses?

1.5 times system pressure Signup and view all the answers

What is the alternative to pressure testing a new purchased hose from an approved vendor?

Operational check using system pressure Signup and view all the answers

What is the consequence of a hose assembly failing the pressure test?

It can be very dangerous to personnel and property Signup and view all the answers

What is the importance of following safety procedures during pressure testing?

To protect personnel and property from potential hazards Signup and view all the answers

When installing hose or hose assemblies, what should be ensured regarding identification markings?

They are visible Signup and view all the answers

What can happen to the length of the hose when pressure is applied?

It changes in length from +2% to -4% Signup and view all the answers

Why should swivel connector nuts be finger-tightened initially?

To avoid stripping threaded areas of fittings Signup and view all the answers

How should the final torque be applied to end fittings?

Using a torque wrench and holding the fitting stationary Signup and view all the answers

Why should the hose be held manually when applying final torque?

To prevent rotation and scoring of the fitting's sealing surface Signup and view all the answers

What should be used to prevent chafing when routing and clamping the flexible hose?

Cushion-type clamps Signup and view all the answers

What should be ensured when supporting the flexible hose or hose assemblies?

That they are not restricted Signup and view all the answers

When flexing is required in an installation, how should the hose be bent?

In the same plane of movement Signup and view all the answers

Study Notes

Calculating Bend Allowances

Use the Bend Allowance Chart or formula to calculate bend allowances
Formula: angle of bend / (2πR) × 360°

Calculating Flats

Calculate flats by subtracting setback for each bend from overall dimension
This leaves the flat dimension

Calculating Overall Length

Divide bent object into flats and bend allowances
Number them progressively (e.g., 1-2, 2-3, 3-4, etc.)
Calculate each length independently, then lay out calculations
Development length equals the total of all lengths

Tube Bending

Objective: obtain smooth bend without flattening tube
Use mechanical or hand-operated tube bender
Minimum bend radius: 2.5 to 3 times the OD

Tube Cutting

Produce square end, free of burrs
Remove burrs from inside and outside the tube using a de-burring tool
Avoid reducing or fracturing the wall thickness of the tubing

Tube Flaring

Preparation: use tube flaring tool to prepare tube ends
Check tube ends for roundness, square cut, and cleanliness
Remove draw marks and scratches

Tube Joint Preparation

Two major tube joints: flared fitting and flareless fitting
Flared fitting: single-flared joint and double-flared joint

Wrinkle or Kink Limitations

Wrinkles or kinks in tubes: limit to 1% of tube OD for working pressures ≥ 500 psi
Limit to 2% of tube OD for working pressures < 500 psi

Typical Repairs

Repair or replace damaged aircraft fluid lines
Use replacement tubing of the same size and material as original
Pressure-test tubing prior to initial installation

Clamps

Maintain minimum clearance of 1/16 in. or 1/4 in. between supports
Use flexible grommets or hose at points where tubing passes through bulkheads

Pressure Test Stands

Hydraulic or pneumatic pressure test fabricated hoses prior to installation
Test to 1.5 times system pressure
New purchased hoses can be operationally checked after installation

Installation Procedures

Remove protective closures from hydraulic lines, hose, or hose assemblies
Install hose or hose assemblies without twisting, chafing, or over bending
Observe bend radius and allow for component movement and possible changes in length

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Description

This quiz covers the calculation of bend allowances in aviation maintenance, using the Bend Allowance Chart or the bend allowance formula.

Calculating Bend Allowance in Aviation Maintenance

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