Eve of War Rotor Blades

[Vizsla]

Any ideas on the eve of war why the RAF should "suddenly" discover that the rotary fleet dont like working in the desert.
Are these the same USA products that the USAF & Marines are using or some cheap import from Taiwan?

[forget]

Is this to do with rotor blade erosion? In a previous life, with a couple of Wessex 60's, we used blade tape. Super size Selloptape which worked very well. Tape eroded - blade OK. Change tape. Is this not still available/used??

[Lu Zuckerman]

The Apache was designed to operate on the European continent fighting a major land war that was predicted to take place in 1988 and the helicopter has not been significantly upgraded to operate in other environments especially the desert.

When the Apache was employed in the Panama invasion the high humidity played havoc on the electronics black boxes. Prior to every flight the mechanics had to dry the black boxes using hair dryers.

Operating in a desert environment may over tax the built in air-sand separators on the engine and it will seriously erode the leading edges and tip of the blades as well as the tail rotors. Sand will get into everything and cause abrasion problems on moving parts and especially the TT straps in the rotorhead. Sand may also cause serious wear problems on the ammunition feed system for the Chain Gun ©. Name the part. If it moves and is exposed it will wear.

:eek:

[AlanM]

I am sure it isn't as bad as is made out - must be the same sand as we flew in back in 91!

Blade tape worked then - are the blades now so different?

The impact of teh sand is seen in a video I took from inside a chinook landing at dusk - lots of tiny "sparks" meant the rotor disc was like a firework!

Oh well - I hope it won't affect there performance/safety.

[B Sousa]

Lu, As to the Apache, there have been many Mods since then. And as to the desert enviornment, it certainly will wear on the blades, but I doubt if there will be enough flight time to warrant but a few replacements.
Spare Parts by the Tons will no doubt be close at hand...

Never fly an "A" model of anything......

[Lu Zuckerman]

The impact of the sand is seen in a video I took from inside a chinook landing at dusk - lots of tiny "sparks" meant the rotor disc was like a firework!

Hopefully Nick Lappos does not read this as he says there is no Corona discharge in the visual spectrum. This spark discharge is true for most helicopters operating in a sandy or dusty environment.

To: Bert

It is true that there have been a lot of mods to the Apache however they are system upgrades and not to those elements subject to sand erosion or abrasion.

It should also be noted that most of the AVIM maintenances and some of the AVUM maintenance is performed by contractors who most likely remained Stateside. This means that the US Armys' maintenance capabilities are very limited.

:cool:

[B Sousa]

"who most likely remained Stateside"

Lu, Im betting that they are closer than you think and making big money. Either way a few blade boxes on a C-17 and you get them in 12 hours.....If the U.S. has learned anything, its the movement of spares in Combat.

[before landing check list]

I cannot speak of experience in the Apache or Chinook, but the Hawks blades have a nickle leading edge and when landing in dust the blades spark due to the dust particals hiting the blades. You will find this mostly below ETL obviously. And the rubber strips worked great until it rained.
j

[Lu Zuckerman]

I got this from Dayton-Granger the manufacturers of static dissipating systems for aircraft and helicopters. The sparks you see at night result from an energy exchange between the airborne particle and the blade. The energy exchange manifests itself as a small spark. The electrical energy from the collective sparks builds up on the blade surface as static electricity. If this static charge can not drain off to the airframe and be dissipated via static wicks then the charge will build to a point where it will bleed into the air as a corona discharge which manifests itself as a glow following the tip path plane. This makes it very difficult to hide a helicopter at night in the desert.

:rolleyes:

[before landing check list]

Lu, then why is it the sparks are still visible (but less due to less sand being blown about) when the helo is at flat pitch and on the ground? When you cover the blades with the rubber strips (for erosion control) the sparking is almost all gone except for the tips that are not covered. You will also see the halo when flying in a dust storm while wearing NVG's. It is not a static discharge causing this.
j

[Letsby Avenue]

The main problem appears to be the tail rotors blades not the MRB - The problem is clearly crews hovering below 500 ft and using the wrong flying technique given the conditions. - IMHO:cool:

[before landing check list]

It is the MRB doing this. And "wrong flying technique"? Have you ever flown one of these helos in the desert? I do not think so.
j

[Lu Zuckerman]

To: before landing check list

Lu, then why is it the sparks are still visible (but less due to less sand being blown about) when the helo is at flat pitch and on the ground?

As it says above sand particles come in many sizes. Consider the desert environment. There is sand everywhere and a great deal of it is entrained in the air we breathe and the air we fly in.

Because of the small size of the entrained particles while at flat pitch and the density of the sand particles in the air the energy exchange (see above) is to a lesser degree and therefor the sparking is less.

Depending on the localized airstream, in which the helicopter is flying in, static electricity, can build up on the blades even if there is no dust entrained in the air. If this charge can not drain down to the fuselage the charge will build up similar to that of a capacitor. When the “capacitor" builds to a specific point at which it can’t store any more static energy it will bleed off the blade tips as visible light.

On those helicopters where the charge can get down to the airframe there are special precautions that must be employed when loading or unloading cargo on a sling. The charge must be grounded before the ground crew can touch the hook. The same is true if picking up someone from the water using the hoist. The sling and hook must be dropped in the water prior to the downed person touching the sling or hoist cable.

It seems you edited your post while I was composing mine.

I am not familiar with the rubber strips you mentioned. If there is minimal sparking or no sparking then there is no energy exchange because of the surface hardness with the rubber strips as compared to a metal blade or, metal erosion strip. If it is in effect sparking at the tips then consider the surface hardness of the tip as compared to the rubber strip(s).

What you see under NVG conditions could be the "sparking" or it could be corona discharge which is caused by static electricity being discharged from the blades. Just imagine an enemy equipped with NVG or IR sights on his gun.

:cool:

[before landing check list]

Lu, all you said was true about static electricty. And you also mentioned the reason for the static discharge wick. If that were the case the thing would quit "sparking" upon touch down, but that is not the case. They still spark, and even more so when pitch is pulled. BUT that is not why they tend to "spark" when hovering close to the ground in the desert. It is because of the sand particals hitting the leading edge which is a metal hybrid. (erosion strip is there for that reason, it erodes) The tail rotor has no such strip thus does not spark. The AS350 is all composite, does not spark. It still has the same static buildup obviously. You still have to discharge it before you touch it before commencing hoist ops. But no "sparks" when flown in the desert enviroment,below ETL and close to the ground. (ie hovering)
j

[helmet fire]

For the Lu induced discussion on blades at night, see the following thread, bear with the banter, there is a lot of information in between:

Night Blade glow (http://www.pprune.org/forums/showthread.php?s=&threadid=18985)

For the original question: The Oz Army revealed significant dust erosion related issues when they first began operating the Black Hawk during a major exercise in 1989. The subsequent mods were later used by the US Army in G1. The mods included elastomeric pitch change links and blade erosion measures. Makes sense in such a dusty country as Oz.

(I wonder if these issues have been considered by the team that recently purchased the Tiger for the Aussies?)

[Lu Zuckerman]

To: helmet fire

Hopefully Nick Lappos does not read this as he says there is no Corona discharge in the visual spectrum. This spark discharge is true for most helicopters operating in a sandy or dusty environment.

In referring to the previous posts on this subject referenced in your above post you will note that I made several comments relative to spark and corona discharge in the visible spectrum and Nick Lappos said I was wrong which is counter to the observations of members contributing to this thread.

Oh well....

:rolleyes:

[headsethair]

From what I know, the UK Apaches are not being used because of a shortage of crews. There's been a spat between CAA and the military over training. As I was told, any UK pilot who trained on the US facility isn't licensed/certified by the CAA for UK ops - and the UK pilots have to use the US training facility because we have nothing big enough in the UK. We apparently don't have a training area large/safe enough for the full range of the laser.
Can't tell you how I heard this and it may be a load of cod's "wallop".

[B Sousa]

If that were in the states the Military would tell the FAA to pound sand. As a Military Pilot here, one does not need an FAA license, just the Military schooling. If you desire to get one its laid out in the regs and simple to do........BUT to have something like the FAA telling the military what to do, I find it could only happen in a place like the UK. What a joke.

[Helinut]

The CAA may think they are god almighty, but they haven't yet got their teeth into military flying ................. It ain't nothing to do with them!:eek:

[helmet fire]

Lu,

what a wonderful way to twist your words.....but you are the master!;) ;)

[Lu Zuckerman]

To: helmet fire

Exactly what words did I twist? I stated that in the previous posts (which you referenced) on the subject of sparking and corona discharge Nick Lappos stated that I was wrong which is contrary to what is being posted in this thread. If you don’t see it that way I’m sorry for posting

:rolleyes: