View Full Version : Fan Blade numbering
319/320
28th Dec 2008, 08:19
Is there a way to determine how mtc numbers the blades after they have been snagged for dings/dents? In our company, they used to number them with a marker after being snagged. They have stopped doing it. How do you know if #15 or #21 or whichever has been blended within limits, and there is a new ding?
HAWK21M
28th Dec 2008, 10:01
Normally the 1st blade is marked near the hub,the rest are numbered in sequence CW.
regds
MEL
As MEL says there is a mark on the shaft adjacent to where the #1 blade goes. They are then numbered CW aft looking forward. So looking into the engine from the front anti-CW.
BTW. Do not assume numbers written on blades correspond to their position as per the AMM. The numbers may have been wriiten to aid blade removal and re-installation and may bear no relation to the actual blade number.
This convention applies to GE/RR etc there may of course be other numbering conventions for other types
Swedish Steve
28th Dec 2008, 18:02
BTW. Do not assume numbers written on blades correspond to their position as per the AMM. The numbers may have been wriiten to aid blade removal and re-installation and may bear no relation to the actual blade number.
Very true. I was once dropped in the sh1t by this. I went out to Karachi with a set of fan blades for a RB211 after a bird strike there. We fitted the blades nbr 1 to 33 ACW as marked on the blades. Their was still fan vibration afterwards and we ended up doing a two engine ferry back to BAH.
On arrival, I was given the fan blade fitment sheet that the engine shop had found. The blades had been balanced on a rig at RR, and the fitting sequence bore no relation to the numbers. Me and 250 Pakistani passengers were not amused.
Piper19
28th Dec 2008, 21:56
I speak for RB211, as I am used to working on these. There is an asterisk on the fan hub where the N°1 blade goes. Then you number them in an anti clockwise direction when looking aft into the engine. Most of the time tere is an arrow next to the asterisk going ACW. The numbering is done before blade removal, so it will only stay the same when no blades are replaced (e.g. dirt removal of blade, lubrication, attrition liner repair...). When blades are replaced, engineers make a new distribution according to moment weights and they will have a paper like "blade 1 fits place 1; blade 2 fits place 3: blade 3 fits place 33,...
So as a pilot, ignore blade numbering.
Btw, numbering fan blades with an alcohol marker is a bad habit I often see. Not good on titanium blades. Better put painters tape on the blade and write on that.
As for your question, once a blade has been blended, it is seen as a serviceable one without limits. If there are limits, the blade will not be on that engine for long ( 1 or 2 flights). Any new dings will create a new situation which has to be looked up in the AMM. This manual states limits for multiple dings on one blade.
Swedish Steve, I had some similar incident. We got a wrong blade distribution faxed. When starting the engine afterwards for the check it was like the wing fell off with a very loud grinding noise, without even fully spooling up. Shutted down the engine and recalled the eicas page showing 5.9 units of vibration!:=
One question regarding those vibration indication values.. what is the norm here, IPS (inches per second) or something manufacturer-specific?
RB Thruster
29th Dec 2008, 08:40
Well said everybody.
No1 blade on RB211 and Trents is marked with an asterisk on the disc next to the slot the blade slides into, then add a piece of masking tape to each blade at the outer end and mark the numbers as you rotate the fan around. Don't mark the blade direct as won't come off!
In the event of a full blade set change then the replacement set should come with a patternation chart, which allocates each replacement blade to a disc slot based on the weight characteristics of each blade - this is created using a special programme in the shop and should ensure that only a trim balance will be needed to balance the fan to AMM limits.
Also when changing blades, don't forget to immobilise the fan!
:ok:
RBT
celtic mech
29th Dec 2008, 17:24
Most engines are, as previously said, numbered CW aft looking fwd....but are Rolls Royce not the opposite to this? Thought the Trents are done ACW aft looking fwd....
N1 Vibes
29th Dec 2008, 22:36
Hello,
convention is blades are numbered as you would see them in 'rotation' as viewed from front looking aft, i.e. first blade to pass is #1, 2nd blade to pass is #2 etc. So for RR enignes with ACW rotation (when viewed from front) number in ACW direction. And North American engines with CW rotation (again when viewed from front) number in CW direction.
For Swedish Steve, it is most likely that you were sent with the engine shop distribution list. This document is where the blades are received for assy of the fan module in a box - with a piece of paper listing 1 - xx pn/sn. Then the blade weights are calculated and re-distributed by computer programme and a new list, or more commonly a new set of numbers are written in on the same sheet of paper next to the orignal 1 - xx numbers. I.e. #1 on original list may be now #14 position and #2 could be #8 and so on.
I have seen it happen a few times that blades have been fitted to the original 1 - xx blade order. This is not truly the fault of the line-engineer, as he would normally not refer to the shop document. The people who provide the list should 're-order' the blade positions on one list before sending out the work instruction.
For Dufo - RB211 data is generally IPS in the test-cell and converted to a/c units on-wing.
Regards,
N1 Vibes
319/320
30th Dec 2008, 11:33
Thanks for all the informative replies. Can you see the asteiric on the hub from standing on the ground during a normal walk around inspection, or do you have to be standing right in the cowl? My eyesight isn't what it used to be!!
celtic mech
30th Dec 2008, 11:39
319/320...Chances are you probably wont see from the ground (well depends on the a/c type)...If you can get into the fan inlet then its no problem finding it. Some engines have the little dimple colored white for ease of identification. The CF6 engine on the 330..you would definately need to climb into the inlet cowl and find the identification mark
Mike Strutter
30th Dec 2008, 14:41
319/320
With the CFM series powerplants which i assume my be fitted to your a/c there is not a asterix but rather a small circle indicating the first blade position. It is easy enough to see.
N1 Vibes
30th Dec 2008, 22:25
Mike,
you need to get in the cowl.
Regards,
N1 Vibes
N1 Vibes
31st Dec 2008, 22:31
....the fan could be windmilling, or the asterisk may be at the top of the rotor, not the bottom where you can see it from the ground and I don't think you can count that qucikly or accurately. For the purpose of precisely identifying a blade - getting in the cowl is much better......
Piper19
2nd Jan 2009, 20:10
You cannot see the asterisk, it's on the rotor hub under the spinner.
cwatters
2nd Jan 2009, 22:10
As an outsider I would have expected each blade to have had a serial number and a log kept of which SN was used in each position. Isn't it like that? What happens when an engine is wrecked, do they have to figure out which blade was where from the damage alone?
celtic mech
2nd Jan 2009, 23:04
The Fan Blade Part Number, Serial Number and Moment Weight are actually laser etched into the blade but its actually in the root section where they attach/slot into the hub. These are recorded at certain intervals...i.e. the likes of a heavy overhaul check where fan blades would be removed from the engine for insection, lubrication etc.
319/320
3rd Jan 2009, 13:33
Ok, thanks again. It's a RR Trent engine. I'm guessing the asterik is under the hub? Just how bad is it for the titanium blades if you mark them with a sharpie? That must be why they don't do it anymore.
lomapaseo
3rd Jan 2009, 13:59
Ok, thanks again. It's a RR Trent engine. I'm guessing the asterik is under the hub? Just how bad is it for the titanium blades if you mark them with a sharpie? That must be why they don't do it anymore
Depends on where you mark them. The lowest stress area is the bottom of the root attachment. But I wouldn't recommend you do any marking with any tool that hasn't been OKd by the manufacturer. You can get away with a variety of markings on titanium in the cold fan section that you can't use on titanium in the hotter sections of the engine. That goes for tools as well
Piper19
4th Jan 2009, 21:53
Indeed as said, at the (invisible) blade root there is the SN, moment weight and overhaul number, which states how many times the blade has been reworked. Each blade is logged as they have a finite lifetime etc...
lomapaseo
5th Jan 2009, 01:13
Each blade is logged as they have a finite lifetime etc...
Interesting, what defines their lifetime in age?
Lightning5
5th Jan 2009, 18:19
CF6-80 Series motors have the #1 fan blade "1" stamped each side of the blade dove tail post on the fan disc. You cannot see it with the spinner on. counting is counterclockwise looking aft and i believe #5 blade is also marked on the spinner disc. my old company used a paint mark on the spinner to indicate#1 fan blade not to be mistaken for the paint mark on the spinner offset hole. This ensures that the spinner goes back onto the correct position on the fan disc. High N1 vibs on these engines was usually corrected by lubing the fan blade dovetail posts on the fan disc as well as lubing the fan blades.
N1 Vibes
5th Jan 2009, 21:51
319/320
on the Trent there is an asterisk on the spinner extension piece, it's next to where all the balance weight screws are fitted. As for sharpies - NO, NO, NO...
For Lomopaseo - the blades are 'lifed' just like other rotating components in the engine, only the blades are normally 'Cat B' lives, not 'Cat A' lives, can be found in Chapter 5 of the Enigne Manual, and they are governed in cycles.
Regards,
N1 Vibes
319/320
13th Feb 2009, 17:16
Okay, I have seen the asterix, fan not spinning, on the hub.
Thanks for the responses from the techies! Better informed.