re-polishing leading edge skin
re-polishing leading edge skin
(OP)
While in HMV environment one customer requested re-polishing of all nose skins on L/E slats, Vertical Stabilizer, Inlet Cowls, to improve appearance (no damage, such as scratches/gouges/nicks, have been noted).
L/E slat nose skin: 0.063" thick, chem milled to 0.040", 7075-T6.
Inlet Cowl lip skin: 0.092" thick, 2219-T62.
Vertical Stabilizer: composite metallic structure, Outer skin is 0.100" thick chem milled, 2024-T3 Clad.
I am looking for a technical argument not to do the re-polishing.
L/E slat nose skin: 0.063" thick, chem milled to 0.040", 7075-T6.
Inlet Cowl lip skin: 0.092" thick, 2219-T62.
Vertical Stabilizer: composite metallic structure, Outer skin is 0.100" thick chem milled, 2024-T3 Clad.
I am looking for a technical argument not to do the re-polishing.





RE: re-polishing leading edge skin
Dik
RE: re-polishing leading edge skin
If the airplane usually has polished L/Es then there should be MM limit on polishing. Maybe the OEM didn't anticipate owners wanting to polish the L/E and so never investigated this ? If there is no limit in the MM you could ask the OEM. Possibly your plane has "after-market" (STC) installed L/Es that are nice and pretty. Then ask the STC holder.
This should give you guidance to go ahead or not.
another day in paradise, or is paradise one day closer ?
RE: re-polishing leading edge skin
- If you are a HMV - 3rd party .. what is the issue ? Mucho billable hours & employing relatively low skill manpower.
- If HMV is part of the same company then the polishing crew will start discovering all types of issues such as pitting, loose rivets, dents, cracks, & will make a mess of the hanger during the exercise - because polishing is messy!
- just indicate to upper management a 'generous' amount of Manhours & Out-date departure delay .. & the problem will go away ..
RE: re-polishing leading edge skin
another day in paradise, or is paradise one day closer ?
RE: re-polishing leading edge skin
B.E.
You are judged not by what you know, but by what you can do.
RE: re-polishing leading edge skin
After several years of polishing, the cladding was worn thru and rampant corrosion became a maintenance nightmare.
As I recall, most Boeing jets with unpainted/polished leading edges do NOT have aluminum... they are stainless steel or titanium.
Many turbine engine inlet lips [heated] that were anodized aluminum also do NOT survive very long due to atmospheric abrasion. A special heat/abrasion resistant 'lip-skin' coating [AMS3604] is applied to eliminate corrosion and maintain a clean/decorative appearance for a extended length of time... at the cost that when this coating is properly applied... it is for all practical purposes permanent.
I THINK that it MIGHT be possible to polish aluminum, then quickly apply a clear conversion coating... such as MIL-DTL-5541 class 3... or a B-52s and KC-135s early on were kept polished to survive in a nuclear environment.
After several years of polishing, the cladding was worn thru and rampant corrosion became a maintenance nightmare.
As I recall, most Boeing jets with unpainted/polished leading edges DO NOT have aluminum skins... they are stainless steel [or titanium?].
Many turbine engine inlet lips [heated] that were anodized aluminum also do NOT survive very long due to atmospheric abrasion: abrasive pitting wears away all anodize finishes sooner or later. A special heat/abrasion resistant 'lip-skin' coating [AMS3604] is applied as a primary [or post-production repair] coating to eliminate corrosion and maintain a clean/decorative appearance for an extended length of time... at the cost that when this coating is properly applied... it is for all practical purposes permanent [touch-up only... stripping VERY difficult].
I THINK that it MIGHT be possible to: [a] polish the aluminum; then [b] quickly apply a clear conversion coating such as MIL-DTL-5541 class 3... or a [clear/un-tinted] silane-based surface prep such as s 3M AC-130 or -131 or PRC-DeSoto EAP-9 or -12; then [c] apply a clear polyurethane topcoat. But I couldn’t fathom a guess as to how-long this coating would maintain the sparking-bright appearance. At least this coating would look polished AND be sorta maintainable.
Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]
RE: re-polishing leading edge skin
RE: re-polishing leading edge skin
OK, I admit it... I tend to go-off-line [into MS word] for longer posts simply because I have 'lost several long drafts' due to computer glitches and unforeseen aws*ts, my part. In this case my haste to cut/paste W/O editing kicked my butt kicked my butt kicked my butt kicked my butt.
Here is what I actually meant to say...
----------
B-52s and KC-135s early on were kept polished to survive in a nuclear [flash] environment. After several years of polishing, the cladding was worn thru and rampant corrosion became a maintenance nightmare [all skins].
As I recall, most Boeing jets with unpainted/polished leading edges DO NOT have aluminum skins... they are stainless steel [or titanium?].
Many turbine engine inlet lips [heated] that were [thick] anodized aluminum also do NOT survive very long due to atmospheric abrasion: abrasive pitting wears away all anodize finishes sooner or later. A special heat/abrasion resistant 'lip-skin' coating [AMS3604] is applied as a primary [or post-production repair] coating to eliminate corrosion and maintain a clean/decorative appearance for an extended length of time... at the cost that when this coating is properly applied... it is for all practical purposes permanent [touch-up only... stripping VERY difficult].
I THINK that it MIGHT be possible to: [a] polish the aluminum; then [b] quickly apply a clear conversion coating such as MIL-DTL-5541 class 3... or a [clear/un-tinted] silane-based surface prep such as s 3M AC-130 or -131 or PRC-DeSoto EAP-9 or -12; then [c] apply a clear polyurethane topcoat. But I couldn’t fathom a guess as to how-long this coating would maintain the sparking-bright appearance. At least this coating would look polished AND be sorta maintainable.
Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]