Compressor Washing

Why Wash Compressors?

When gas turbine engines are run, they become fouled with airborne contaminants such as oil, soot, unburned fuel, soils and salt which encrust compressor components. Power loss follows as the compressor loses efficiency and degrades the performance of the engine, leading to higher operating temperatures, increased fuel consumption and shorter component life.

Some engines are more prone to fouling than others – low flying over land or sea, or operating in contaminated air, have led to helicopter engines and industrial engines traditionally needing cleaning – but nowadays it is recognised that all engines foul to some extent; for example, oil leakage and subsequent fouling can happen on any engine type. Contamination can also be caused by ingestion of exhaust gases from other aircraft during prolonged waits for takeoff clearance.

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Lockheed’s SkunkWorks

The following are from Kelly Johnson of Lockheed’s SkunkWorks:

  1. The Skunk Works manager must be delegated practically complete control of his program in all aspects. They should report to a division president or higher.
  2. Strong but small project offices must be provided both by the military and industry.
  3. The number of people having any connection with the project must be restricted in an almost vicious manner. Use a small number of good people (10% to 25% compared to the so-called normal systems).
  4. A very simple drawing and drawing release system with great flexibility for making changes must be provided. Read More

Acronyms


AGL means above ground level.

ALS means approach light system.

ASR means airport surveillance radar.

ATC means air traffic control.

CAS means calibrated airspeed

CAT II means Category II.

CONSOL or CONSOLAN means a kind of low or medium frequency long range navigational aid.

DH means decision height.

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Bruhn Table of Contents

Analysis and Design of Flight Vehicle Structures (Bruhn)

TABLE OF CONTENTS

Al The Work of the Aerospace Structures Engineer.
STATICALLY DETERMINATE STRUCTURES
(Loads, Reactions, Stresses, Shears, Bending Moments, Deflections)
A2 —- Equilibrium of Force Systems. Truss Structures. Externally Braced Wings. Landing Gear.
A3 —- Properties of Sections – Centroids, Moments of Inertia, etc.
A4 —- General Loads on Aircraft.
A5 —- Beams – Shear and Moments. Beam – Column Moments.
A6 —- Torsion – Stresses and Deflections.
A7 —- Deflections of Structures. Castigliano’s Theorem. Virtual Work. Matrix Methods.

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Bruhn Index

Analysis and Design of Aircraft Structures
Index:

Accelerated Motion of Rigid Airplane ……………………………………..A4.8
Aircraft Bolts………………………………………………………………………D1.2
Aircraft Nuts ………………………………………………………………………D1.2
Aircraft Wing Sections – Types………………………………………………A19.1
Aircraft Wing Structure: Truss Type………………………………………..A2.14
Air Forces on Wing……………………………………………………………. A4.4
Allowable Stresses (and Interactions)………………………………………C11.36
Analysis of Frame with Pinned Supports…………………………………..A9.16

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Misc Bonding Notes

Sandwich Panel Bonding

Prior to bonding loosely assemble panels together ensuring all joins mate fully. All bonded joints will require clamping during cure. Clamps should not apply pressure to the joint directly, but to the panel surface adjacent to each joint. Ensure clamp pressure is spread evenly down the panel. Prepare tooling as required to ensure corners will be cured under pressure 90 ° to each other. Structure may be bonded in stages to improve ease of manufacture.

Clean all mating surface prior to bonding by removing loose material. Use only oil-free compressed air. Lightly abrade bonding surface of panel skins (tongue sections) using 240 grit paper or 220 grit aluminium oxide grit blast. Protect non-bonding surfaces and core against sanding/grit blast damage.

Remove all dust using oil-free compressed air and wipe bonding surfaces clean using a clean white cloth moistened with MEK. Wipe in one direction only using a new section of cloth for each wipe. Wipe exposed core clean using MEK to remove surface contaminants. Do not allow MEK to pool on surface. Protect prepared surfaces from contamination.

All panel intersections are to be bonded with Hysol EA9309.3NA adhesive. Prepare adhesive in accordance with EA9309.3NA data sheet. A small amount, maximum 5% by weight of phenolic microballoon may be used to thicken adhesive if required. Ensure all bonding is carried out in a dust-free environment. Personnel handling cleaned and surface prepared components are to wear disposable gloves.

Apply EA9309.3NA to the core and skin surfaces of all mating components (tongues and grooves). Apply sufficient adhesive to the core components to fill exposed cells. Sufficient adhesive is to be applied to the skin surfaces to ensure squeeze-out of the adhesive occurs during bonding.

Clamp panels together, progressively increasing clamping pressure until joints are held solidly and a square assembly is achieved. Clamp only using hand force to tighten. Do not over clamp.

Form a fillet of adhesive along the inner surface of each joint nominally 2mm x 2mm wide except along the joints where internal reinforcing angles are to be installed. Ensure exposed core of finger joints are filled with adhesive. Clean up remaining adhesive using a cloth moistened with MEK prior to the adhesive curing. Retain a small amount of adhesive on a separate piece of aluminium to verify proper cure.

Cure in accordance with Hysol EA9309.3NA data sheet. Remove clamps after cure and check integrity of the bond by applying slight pressure to the joints and check the squareness of the assembly.

Bonding Internal Reinforcing Angles

Lightly abrade bonding surface of panel skins and angle sections using 240 grit paper or 220 grit aluminium oxide grit blast. Protect non-bonding surfaces and core against sanding/grit blast damage.

Remove all dust using oil-free compressed air and wipe bonding surfaces clean using a clean white cloth moistened with MEK. Wipe in one direction only using a new section of cloth for each wipe. Continue wiping until no discolouration of the cloth occurs. Do not allow MEK to pool on surface.

Wipe each bonding surface with Turco WO1 using a clean white cloth to apply the etch primer. Wash primed surfaces with clean water. Protect prepared surfaces from contamination.

Reinforcing angles are to be bonded with Hysol EA9309.3NA adhesive. Prepare adhesive in accordance with EA9309.3NA data sheet. Ensure all bonding is carried out in a dust-free environment. Personnel handling cleaned and surface prepared components are to wear disposable gloves.

Apply EA9309.3NA to the bonding surfaces of the reinforcing angles Sufficient adhesive is to be applied to the angle surfaces to ensure squeeze-out of the adhesive occurs during bonding.

Clamp angles in place, progressively increasing clamping pressure until angles are held solidly. Clamp only using hand force to tighten. Do not over clamp.

Form a fillet of adhesive along the edges of each clamp flange. Clean up remaining adhesive using a cloth moistened with MEK prior to the adhesive curing. Retain a small amount of adhesive on a separate piece of aluminium to verify proper cure.

Cure in accordance with Hysol EA9309.3NA data sheet. Remove clamps after cure and check integrity of the bond by tap testing for voids. No voids permitted.

Edge Filling Sandwich Panels

All exposed core edges are to be filled with Hysol EA9309.3NA/Microballoon mix after assembly.

Push the core back from the edge of the panel skins approximately 2-3mm.

Prepare adhesive in accordance with EA9309.3NA data sheet. A small amount, maximum 15-20% by volume of phenolic microballoon may be used to thicken adhesive if required.

Fill the gap between the panel skins flush with the edge of the panel using the adhesive mix. Clean up remaining adhesive using a cloth moistened with MEK prior to the adhesive curing.

Cure in accordance with Hysol EA9309.3NA data sheet.

Bonding Non-Structural Edging Angles

Remove all dust using oil-free compressed air and wipe bonding surfaces clean using a clean white cloth moistened with MEK. Wipe in one direction only using a new section of cloth for each wipe. Continue wiping until no discolouration of the cloth occurs. Do not allow MEK to pool on surface.

Edging angles are to be bonded with Hysol EA9309.3NA adhesive. Prepare adhesive in accordance with EA9309.3NA data sheet. Ensure all bonding is carried out in a dust-free environment. Personnel handling cleaned and surface prepared components are to wear disposable gloves.

Apply EA9309.3NA to the bonding surfaces of the edging angles Sufficient adhesive is to be applied to the angle surfaces to ensure squeeze-out of the adhesive occurs during bonding.

Clamp angles in place, progressively increasing clamping pressure until angles are held solidly. Clamp only using hand force to tighten. Do not over clamp.

Form a fillet of adhesive along the edges of each clamp flange. Clean up remaining adhesive using a cloth moistened with MEK prior to the adhesive curing.

Cure in accordance with Hysol EA9309.3NA data sheet. Remove clamps after cure and check integrity of the bond by applying light pressure to the angles.

Bruhn Errors

Page A4.3, column 1, equation 3, should read

“V^2 – Vo^2 = 2as”
(first velocity term must be squared)

And then there’s the previously mentioned page B1.8, Equation 3,

“…= f/F0.7 + (3/7)*(f/F0.7 )^n

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