Autorotate
4th Sep 2004, 20:31
Another story from the mag that thought might be of interest to members.
Autorotate.
-------------------------------------------
CARING FOR YOUR AIRCRAFT – WINDOWS
By: Bill Reid
Photos: Toby Reid & Neville Dawson
I recently attended the annual HAI Convention in Dallas. For someone who had never been before it was awe inspiring to see the World’s latest and greatest helicopters all under one roof. They were all polished up and glittering under the special lighting effects that their respective marketing departments had devised. Imagine my disappointment on seeing many of these aircraft had badly scratched windscreens, the cause of this damage being simply, poor cleaning technique.
Helicopters, because of the nature of their low level operations tend to collect dust and dirt; more so than their fixed wing cousins, and I am often amused by various people’s attitude to cleaning helicopter windows. So many pilots think it is beneath them to pick up a rag, while some engineers think that while they may have to wipe up oil they’ll be blowed if they are going to clean the pilot’s perspex for him. Often the job gets left to the least experienced personnel, the hangar boy or labourer, who has no specific training in how fragile the material can be.
Personally I dislike other people touching my aircraft’s windows. It is better to tell them before it is too late not to help defrost frozen windows or wipe mist off the inside, particularly if they have a metal watchstrap, diamond rings or even sharp fingernails. It’s always better to wait and let the heater or air-conditioning unit clear the windows anyway.
When it comes time to clean the windows always start with a fresh water rinse. This helps soften any insects and dust particles before you start wiping with a cloth. Next get a bucket of hot water, add some mild detergent and with a soft spongy cloth gently wash the windows. I have found “Turtle Wax” wash and wax to be an ideal product for this phase. It is good at removing insects, grime and leaves no watermarks on drying as long as it is rinsed property.
Remember to rinse regularly after every 2 or 3 windows especially if working in direct sunlight as the soap dries very quickly then becomes very difficult to polish off.
If no further polishing is necessary, the best way to dry the windows after rinsing is to go flying. If it is necessary to wipe them dry, chamois leather is the next best thing. Remember though to make sure the cloth is absolutely clean.
During all the different steps of aircraft window cleaning every time you drag a rag or cloth across the surface no matter how carefully you do it you will cause minute scratches. Most people I have spoken to on the topic agree that the best way for these scratches to run is vertically. Horizontal ones look too much like powerlines and circular ones are annoying when flying into the sun.
Choosing a good polish is the next step. When I was young my father owned a fleet of Bell 47’s and as Hangar rat it was my job to keep them clean. I cannot think of any aircraft in the history of aviation that had a bigger single Perspex molding. My father had been a fighter pilot in WWII and he was a stickler for having clean windows. It was as if any bug stuck on the screen might suddenly turn into a ME 109 or FW 190. His favourite polish was a dreadful product called mirrorglaze that always used to leave a greasy
residue that was virtually impossible to remove without using an entire bale of cheesecloth.
Then one of his pilots introduced me to pledge. It was so easy, just spray it on, a quick wipe off and the job was done. Only trouble was the old man caught me using it one day and blew his stack. He said that it built up a residue and that in damp conditions it caused much worse misting that was virtually impossible to remove. So it was back to mirrorglaze and elbow grease.
Once I had left the roost and got my first flying job (Bell 47 still) I decided that pledge was the story again until guess what, flying on a misty rainy day I discovered that I could not de-fog the inside of the bubble. The old man was right, but I was determined not to go back to Mirrorglaze. Help came from one of NZ’s early aviation pioneers Merv Dunn. Merv taught me you can get away with using pledge two or three times on the inside of the windows, after that a scum builds up that needs removing with a pre polish cleaner.
On the front window of the Aztec that Merv was flying at the time, he would use a hard wax, you know the type that comes in a round tin. It really made the rain drops bead off beautifully.
Finding a polish that you like is really a matter of trial and error, but be sure to test what you buy on a piece of waste Perspex first. Do not always trust so called specialist aircraft products. Some of them leave the windows looking worse than when you started; the best products are the ones with an anti static agent.
Selecting the best rags to use is equally important. I like cotton singlets the best, however a cheaper alternative is Mutton or cheese cloth but try and get the pre washed variety as the new product tends to be a bit greasy. If you are using old clothes cut up for rags, double check that there are no buttons, collars, labels, etc that will scratch. Also don’t hesitate to throw the rag away and get another one if you drop it on the ground half way through the job. Remembers it only takes one grain of sand to put a scratch in a critical vision area and ruin a very expensive windscreen.
You will need a minimum of 3 rags to do a good job. One to apply the polish, one to get the majority of the polish off and one to buff it up. When cleaning the interior windows start at the top and work your way down. The chin windows should always be left until last, as they always seem to collect the most dust and dirt. The rags will either have to be washed or thrown away afterwards. Make sure on the final polish that you get all the polish out of the corners and all the nooks and crannies. Nothing looks worse than smudges of product left in these areas.
It does not take long to give your windows a quick wash every morning and you will find that if you use a good wash and wax liquid that you will only have to polish them about once a week.
TOO LATE THE WINDOW IS SCRATCHED
Despite best endeavors there will be times that windows will get scratched and damaged. It is often possible to minimize this with a little hard work and patience. Minor scratches can be removed with a mild liquid abrasive such as Brasso or automotive cutting creams. Some people even say toothpaste works though I have never tried it. Use a small piece of towelling rag and work in the opposite direction to the scratch for several minutes and finish off with your normal polish.
Deeper scratches may require the use of a specialised scratch removal kit such as Micromesh or Polysand. These kits consist of a series of very fine sandpaper’s ranging in grit from 2400 to 12,000. Each grade requires you to work in the opposite direction from the last. I have had some success with these products though not on deep scratches in critical vision areas because some distortion occurs.
If you have been unlucky enough to be hit with paint overspray as often seems to be the case when parked in or near maintenance hangars as a first step try Brasso or a proprietary aircraft window scratch remover. depending on the type of product your aircraft’s windows are made of; they could be Lexan, Acrylic, Lucite, Plexiglass, etc. You may be able to use a rag lightly moistened with paint thinner. Seek your engineer’s advice as some formulations will soften and craze the plastic very quickly. Again, experiment on an old piece of the same product first.
PREVENTATIVE ACTIONS
The best defence is to educate people not to spray paint in the vicinity of uncovered aircraft. Remember rotor blades suffer too. It never ceases to amaze me how many experienced aircraft engineers do it. I think a lot of them were brought up on Intra dopes and laquers that dried very quickly and any overspray that landed outside the target area just wipes off as a fine powder dust. Today’s more complex 2 pot finishes stay wet suspended in the air for several minutes after leaving the gun and bonds to any surface that they come into contact with.
Next time you discover you cannot get a rag to flow over your windscreen because it is covered in minute particles of paint get the culprit to clean it for you, maybe it will teach them not to do it again.
I know of people using power buffs or polishers to speed up the process of restoration but be very careful, it is really a job for an expert. The potential for doing lasting damage is great and it would be very easy to get deep swirl marks.
If your machine is fitted with windscreen wipers only use them as a last resort and only when it is raining hard enough to lubricate the screen properly. Even on the larger helicopters fitted with toughened glass
front window scratching occurs. Make it a policy to always clean the wiper blades of dust and dirt on every preflight inspection. Sliding side screens are another problem area. They trap dust and sand and soon scratch the window area they slide over. Have the engineers take them out periodically and clean and polish the edges that make contact.
When choosing replacement windows give some thought to ordering light tinted windows. They resist sun crazing better than clear Perspex although you do sacrifice some night vision. Similarly for those people that operate French equipment you will find that windows sourced from American market suppliers will last a lot longer than the OEM Product that seems to craze and go yellow very quickly in our harsh ozone depleted atmosphere.
If you are not fortunate enough to be able to hangar your aircraft and decide to use a cover to stop sun damage be extra careful not to get dirt trapped under it as the end result can be the same, window replacement.
Never neglect to repair or replace damaged windows immediately. I get cold shivers down my spine every time I see an aircraft being operated with cracked or broken Perspex. Some years ago I was taught a very expensive lesson. I was flying a Hughes 500 that had a 3 inch crack in a back window staring from a snapvent hole. I thought it was nothing and would have my engineer fix it at the next 100hr inspection. One hot sunny afternoon while cruising along at 130kts, enjoying the view I pulled open the front air vent which slightly pressurized the cabin. There was an almighty bang followed by a shuddering in the controls. I landed as soon as possible to find the cracked back window on my side had completely gone. Closer inspection revealed one main rotor bade had serious damage, a series of deep dents ran down the tail boom and one end Plate of the horizontal stabilizer had been destroyed. I found it hard to believe that a thin piece of plastic could do so much damage. I guess I was very lucky that it did not take my tail rotor out.
Another problem I have noticed is window edges that have come into contact with pain stripper. Apart from looking disgusting these windows will be severely weakened and should be replaced.
THE HAZARDS INVOLVED IN CLEANING WINDOWS
One would think that cleaning windows would be a relatively safe pastime and that the worst thing that might happen is perhaps you could slip and fall off a ladder or squirt pledge in your eyes, however I know of at least two serious accidents that have happened. The first involved a good friend of mine who started up his machine on a cold morning and then decided he had better defrost the bubble before he went flying. He found an old aluminum cooking pot, filled it with warm water and threw it over the ice. Problem was he let go of the pot and it went straight up into the blades and damaged one beyond repair. It was a very expensive lesson, but luckily no one was hurt. In the second incident a pilot lost his life when he landed to wipe some insects off his windscreen. Instead of waiting for the blades to stop turning he climbed up and was promptly decapitated. I imagine whoever got the job of eventually cleaning those windows had more than a few insects to worry about!
LOOK AFTER THE HELICOPTER AND THE HELICOPTER WILL LOOK AFTER YOU
That’s my philosophy and I get very annoyed when I see a rough looking machine and the operator says “Ah its only cosmetics, mechanically it’s really sound”. That’s bull****, why should anyone believe that if someone is too lazy or hard up to keep the airframe tidy, they will be any more fussy with the mechanical components. These people would do themselves and the whole helicopter industry a favour if they either lifted their standards.
Autorotate.
-------------------------------------------
CARING FOR YOUR AIRCRAFT – WINDOWS
By: Bill Reid
Photos: Toby Reid & Neville Dawson
I recently attended the annual HAI Convention in Dallas. For someone who had never been before it was awe inspiring to see the World’s latest and greatest helicopters all under one roof. They were all polished up and glittering under the special lighting effects that their respective marketing departments had devised. Imagine my disappointment on seeing many of these aircraft had badly scratched windscreens, the cause of this damage being simply, poor cleaning technique.
Helicopters, because of the nature of their low level operations tend to collect dust and dirt; more so than their fixed wing cousins, and I am often amused by various people’s attitude to cleaning helicopter windows. So many pilots think it is beneath them to pick up a rag, while some engineers think that while they may have to wipe up oil they’ll be blowed if they are going to clean the pilot’s perspex for him. Often the job gets left to the least experienced personnel, the hangar boy or labourer, who has no specific training in how fragile the material can be.
Personally I dislike other people touching my aircraft’s windows. It is better to tell them before it is too late not to help defrost frozen windows or wipe mist off the inside, particularly if they have a metal watchstrap, diamond rings or even sharp fingernails. It’s always better to wait and let the heater or air-conditioning unit clear the windows anyway.
When it comes time to clean the windows always start with a fresh water rinse. This helps soften any insects and dust particles before you start wiping with a cloth. Next get a bucket of hot water, add some mild detergent and with a soft spongy cloth gently wash the windows. I have found “Turtle Wax” wash and wax to be an ideal product for this phase. It is good at removing insects, grime and leaves no watermarks on drying as long as it is rinsed property.
Remember to rinse regularly after every 2 or 3 windows especially if working in direct sunlight as the soap dries very quickly then becomes very difficult to polish off.
If no further polishing is necessary, the best way to dry the windows after rinsing is to go flying. If it is necessary to wipe them dry, chamois leather is the next best thing. Remember though to make sure the cloth is absolutely clean.
During all the different steps of aircraft window cleaning every time you drag a rag or cloth across the surface no matter how carefully you do it you will cause minute scratches. Most people I have spoken to on the topic agree that the best way for these scratches to run is vertically. Horizontal ones look too much like powerlines and circular ones are annoying when flying into the sun.
Choosing a good polish is the next step. When I was young my father owned a fleet of Bell 47’s and as Hangar rat it was my job to keep them clean. I cannot think of any aircraft in the history of aviation that had a bigger single Perspex molding. My father had been a fighter pilot in WWII and he was a stickler for having clean windows. It was as if any bug stuck on the screen might suddenly turn into a ME 109 or FW 190. His favourite polish was a dreadful product called mirrorglaze that always used to leave a greasy
residue that was virtually impossible to remove without using an entire bale of cheesecloth.
Then one of his pilots introduced me to pledge. It was so easy, just spray it on, a quick wipe off and the job was done. Only trouble was the old man caught me using it one day and blew his stack. He said that it built up a residue and that in damp conditions it caused much worse misting that was virtually impossible to remove. So it was back to mirrorglaze and elbow grease.
Once I had left the roost and got my first flying job (Bell 47 still) I decided that pledge was the story again until guess what, flying on a misty rainy day I discovered that I could not de-fog the inside of the bubble. The old man was right, but I was determined not to go back to Mirrorglaze. Help came from one of NZ’s early aviation pioneers Merv Dunn. Merv taught me you can get away with using pledge two or three times on the inside of the windows, after that a scum builds up that needs removing with a pre polish cleaner.
On the front window of the Aztec that Merv was flying at the time, he would use a hard wax, you know the type that comes in a round tin. It really made the rain drops bead off beautifully.
Finding a polish that you like is really a matter of trial and error, but be sure to test what you buy on a piece of waste Perspex first. Do not always trust so called specialist aircraft products. Some of them leave the windows looking worse than when you started; the best products are the ones with an anti static agent.
Selecting the best rags to use is equally important. I like cotton singlets the best, however a cheaper alternative is Mutton or cheese cloth but try and get the pre washed variety as the new product tends to be a bit greasy. If you are using old clothes cut up for rags, double check that there are no buttons, collars, labels, etc that will scratch. Also don’t hesitate to throw the rag away and get another one if you drop it on the ground half way through the job. Remembers it only takes one grain of sand to put a scratch in a critical vision area and ruin a very expensive windscreen.
You will need a minimum of 3 rags to do a good job. One to apply the polish, one to get the majority of the polish off and one to buff it up. When cleaning the interior windows start at the top and work your way down. The chin windows should always be left until last, as they always seem to collect the most dust and dirt. The rags will either have to be washed or thrown away afterwards. Make sure on the final polish that you get all the polish out of the corners and all the nooks and crannies. Nothing looks worse than smudges of product left in these areas.
It does not take long to give your windows a quick wash every morning and you will find that if you use a good wash and wax liquid that you will only have to polish them about once a week.
TOO LATE THE WINDOW IS SCRATCHED
Despite best endeavors there will be times that windows will get scratched and damaged. It is often possible to minimize this with a little hard work and patience. Minor scratches can be removed with a mild liquid abrasive such as Brasso or automotive cutting creams. Some people even say toothpaste works though I have never tried it. Use a small piece of towelling rag and work in the opposite direction to the scratch for several minutes and finish off with your normal polish.
Deeper scratches may require the use of a specialised scratch removal kit such as Micromesh or Polysand. These kits consist of a series of very fine sandpaper’s ranging in grit from 2400 to 12,000. Each grade requires you to work in the opposite direction from the last. I have had some success with these products though not on deep scratches in critical vision areas because some distortion occurs.
If you have been unlucky enough to be hit with paint overspray as often seems to be the case when parked in or near maintenance hangars as a first step try Brasso or a proprietary aircraft window scratch remover. depending on the type of product your aircraft’s windows are made of; they could be Lexan, Acrylic, Lucite, Plexiglass, etc. You may be able to use a rag lightly moistened with paint thinner. Seek your engineer’s advice as some formulations will soften and craze the plastic very quickly. Again, experiment on an old piece of the same product first.
PREVENTATIVE ACTIONS
The best defence is to educate people not to spray paint in the vicinity of uncovered aircraft. Remember rotor blades suffer too. It never ceases to amaze me how many experienced aircraft engineers do it. I think a lot of them were brought up on Intra dopes and laquers that dried very quickly and any overspray that landed outside the target area just wipes off as a fine powder dust. Today’s more complex 2 pot finishes stay wet suspended in the air for several minutes after leaving the gun and bonds to any surface that they come into contact with.
Next time you discover you cannot get a rag to flow over your windscreen because it is covered in minute particles of paint get the culprit to clean it for you, maybe it will teach them not to do it again.
I know of people using power buffs or polishers to speed up the process of restoration but be very careful, it is really a job for an expert. The potential for doing lasting damage is great and it would be very easy to get deep swirl marks.
If your machine is fitted with windscreen wipers only use them as a last resort and only when it is raining hard enough to lubricate the screen properly. Even on the larger helicopters fitted with toughened glass
front window scratching occurs. Make it a policy to always clean the wiper blades of dust and dirt on every preflight inspection. Sliding side screens are another problem area. They trap dust and sand and soon scratch the window area they slide over. Have the engineers take them out periodically and clean and polish the edges that make contact.
When choosing replacement windows give some thought to ordering light tinted windows. They resist sun crazing better than clear Perspex although you do sacrifice some night vision. Similarly for those people that operate French equipment you will find that windows sourced from American market suppliers will last a lot longer than the OEM Product that seems to craze and go yellow very quickly in our harsh ozone depleted atmosphere.
If you are not fortunate enough to be able to hangar your aircraft and decide to use a cover to stop sun damage be extra careful not to get dirt trapped under it as the end result can be the same, window replacement.
Never neglect to repair or replace damaged windows immediately. I get cold shivers down my spine every time I see an aircraft being operated with cracked or broken Perspex. Some years ago I was taught a very expensive lesson. I was flying a Hughes 500 that had a 3 inch crack in a back window staring from a snapvent hole. I thought it was nothing and would have my engineer fix it at the next 100hr inspection. One hot sunny afternoon while cruising along at 130kts, enjoying the view I pulled open the front air vent which slightly pressurized the cabin. There was an almighty bang followed by a shuddering in the controls. I landed as soon as possible to find the cracked back window on my side had completely gone. Closer inspection revealed one main rotor bade had serious damage, a series of deep dents ran down the tail boom and one end Plate of the horizontal stabilizer had been destroyed. I found it hard to believe that a thin piece of plastic could do so much damage. I guess I was very lucky that it did not take my tail rotor out.
Another problem I have noticed is window edges that have come into contact with pain stripper. Apart from looking disgusting these windows will be severely weakened and should be replaced.
THE HAZARDS INVOLVED IN CLEANING WINDOWS
One would think that cleaning windows would be a relatively safe pastime and that the worst thing that might happen is perhaps you could slip and fall off a ladder or squirt pledge in your eyes, however I know of at least two serious accidents that have happened. The first involved a good friend of mine who started up his machine on a cold morning and then decided he had better defrost the bubble before he went flying. He found an old aluminum cooking pot, filled it with warm water and threw it over the ice. Problem was he let go of the pot and it went straight up into the blades and damaged one beyond repair. It was a very expensive lesson, but luckily no one was hurt. In the second incident a pilot lost his life when he landed to wipe some insects off his windscreen. Instead of waiting for the blades to stop turning he climbed up and was promptly decapitated. I imagine whoever got the job of eventually cleaning those windows had more than a few insects to worry about!
LOOK AFTER THE HELICOPTER AND THE HELICOPTER WILL LOOK AFTER YOU
That’s my philosophy and I get very annoyed when I see a rough looking machine and the operator says “Ah its only cosmetics, mechanically it’s really sound”. That’s bull****, why should anyone believe that if someone is too lazy or hard up to keep the airframe tidy, they will be any more fussy with the mechanical components. These people would do themselves and the whole helicopter industry a favour if they either lifted their standards.