737 800 fan blades and icy tail.
 

Hello all,

I see lots of pilots routinely turning fan blades on the walk around, is there any sense or reasoning for this?

Also what's the reason we get that little bit of ice forming on the vertical stab base after a long cold cruise?

Many thanks

Interesting questions, especially considering some of your other posts...e. g. 737 bleed config for G/A, TRE/TRI requirements, etc etc...

Turning fan blades is easy and quick and satisfying that no odd clicks are heard as well as adjusting the reflected light on the blade leading edges to see if abnormal FOD damage is present. It also helps one peek behind the fan deeper into the engine for anything amiss.

Not just on 73s but any high bypass engine:
To make sure the N1 spool is free to move and there is not a puddle of ice locking it, (first flight of the day), or some FOD.

A spinning spool allows you to see the stator vanes and the compressor intake behind the fan more easily.

Ditto to see the vanes in front of the turbine at the rear.

Ditto to see the condition of the rubbing seal strip round the edge of the fan.

The fin will have been cold soaked during the cruise and if the aircraft desends through moisture, ice may form. The base of the fin area might be aerodynamically 'quiet', so perhaps not enough airflow to disperse any ice, or more likely: the ice may form on the ground during the taxi in to the gate. A similar thing sometimes happens to the landing gear and the lower surface of the wing, under the the fuel tanks.

To add to all of that how else would you know about fan blade icing on the rear of the blade if you didn't touch it...?

In cold climates you may have a significant amount of ice on the fan blades if the engine covers weren't put on over night. Even on routine turnarounds you can find a smaller amount of ice accretion on the fan blades that built up during approach/taxi in.

So to avoid anymore unhelpful and sarcastic comments I shall add to my initial question.

I have been flying (and training) on the 800 for a few years now and have been taught to rotate the fan on every walk around by a few trainers for some of the reasons stated above. I was however told not to put my hands anywhere near the fan in recent times by a very experienced LTC, TRE and senior examiner. This confused me somewhat and caused me to seek clarification and learn something perhaps which might benefit my understanding.

I do check for ice on the fan blades in icing conditions but I don't turn the fan to do so.

I hope now you can understand the relavence of my questions.

What reason did he give you this experienced chap?
I have come across lots of techniques, opinions, pet peeves of various trainers. I listen, let it pass through the BS filter, either discard it or try to remember.

I have my own things, such as not walking in to the wheel well. Don't like the idea of walking into a gas chamber of Skydrol fumes (or worse, a jet). We've had an incapacitation as a result of it. I know what the book says, but no thanks. I can spot a leak by seeing wet ground underneath instead.

Just that he didn't think it was safe or necessary to check and that leaning on the acoustic lining regularly would cause problems.

Why would you need to 'lean on the acoustic lining'

It's not like you have to reach very far ?

Is your senior trainer very overweight? Too many trainers have their own "individual SOP's" that aren't based on anything factual! As mentioned above, apply your bull**** filter.

Rotating the fan provides the following assurances:

1. The fan assembly actually moves.
2. A confirmation of the absence of an unacceptable amount of ice.
3. You can see the inside of the bypass duct to confirm there is no debris or birds etc.
4. That all the compressor inlet and guide vanes are free from obvious damage and no obvious ingestion has taken place.
5. As the blades pass, they all look equal (ish) and there are no obvious buckles or dings.

That little area of ice at the base of the stab is were there is a big metal spar right under the skin where the fin attached to the fuselage. This coldsoaks in the cruise but has enough mass that unlike the skin and other lighter components in the tail structure it does not always warm above freezing up during the descent and so frost condenses on it on the ground.
You'll sometimes see similar effects elsewhere on the airframe (usually on the wing) where heavier structure lies close under the skin.

And if you cannot reach it? (e.g. 757/767)

@ testpanel, OK I could have phrased that better - I meant that I was not talking specifically about 737s, about which I know very little. How do you check the fan on 757/767 then ?

We were once told about an engineer who was working on a fan engine, removing the P1 probe. A part of the probe assembly fell back down the mounting hole and he put his finger in to try to retreive it, upon which the fan, (which was rotating due to the wind), cut his finger clean off !!

Perhaps this is what you were being warned about, but there is no such danger from gently grasping and turning a fan blade from the front - (just don't get your skin jammed between the tip of a blade and the abradable seal).

If, due to the wind the fan is turning any faster than very slow, don't touch it at all - there can be a lot of energy in a rotating spool and you could damage your hand.

As for damaging the acoustic lining, I don't know about Boeing, but on Airbus you would have to do something extreme to even make a mark. What the hell was your instructor doing?

In my experience, walkarounds are notoriously badly taught - if they are even taught at all. (In all my Airbus flying I have never been shown what to do by anybody), but your FCOM should have detailed instructions about what to do and look for.

He was right. My sciatica is a nightmare.

Yes, 5 by 5 now, thanks a bunch. Just to clarify: you're an instructor yourself (for a few years) but another instructor (just one) tells you something with (presumably) no backing other than his own opinion, and you're suddenly all confused and discombobulated? This guy really tell you to not go "anywhere near the fan"? I have a sense (hope?) you're putting us on.

Not that there's anything wrong with that...

Is it wrong to question what you know occasionally? Many times now I have questioned what I know, come on here for support and learned something new which has changed my understanding. Maybe I shouldn't bother.

A few years back I was on a Delta flight from LAX to ATL on an old L-1011. And just as the flight was passing east over the CA/AZ border, the center engine experienced a compressor failure that caused the entire aircraft to shake violently. We dropped altitude and returned to make a safe emergency landing at LAX. So everything worked out OK.

The question I have is how could a pilot perform a pre-flight check of an engine that is located like the center engine of an L-1011 or an MD-11?

They didn't........

So I have checked the company training documentation, FCOM and a video produced by Boeing on how to conduct the preflight inspection and none say you should rotate the fan.

Guess that settles it, don't nobody go near any of them fans again.

What does the engine manufacturer say?

Engine manufacturers tell you how ....... Installers tell you when

Well, there might be a live magneto and if it kicks, you could lose your arm. :E

OP:
Even cadets know that you should check the back of the fans for icing in winter conditions. The ONLY way to do so is by tactile check. ( most fan icing is clear ice, as you as trainer undoubtly know).

What that TRE told you is not only rubbish ('causing damage?!), he is telling you something to omit which can cause serious consequences to the safety of the aircraft and operation.

The hand rotating of the fan is someone's genius idea that is not supported by the manufacturer of the engine or the airframes (airbus or Boeing)

Nowhere will you find a procedure that says grab the fan and give it a whirl on the walk around.

As someone rightly pointed out it can't be such a big issue because it can't be done on the bigger engines that you can't reach or on the cfm56 (or any other engine you can reach) when there is a breeze and the fan is windmilling.

Fill your boots if that gives you a warm and fuzzy but don't label as dangerous or irresponsible (or fat!) those that don't agree with this home made procedure.

I would be far more concerned for them to look through the fan at the stationary core vanes but that task again is up to the installer based on experience with type and operation (the when part).

I trying not to infer what is required, but only what to look for if you care to look

So, in other words, because something cannot be checked SOMETIMES, it shouldn't be checked EVER? Or, because something can't be checked on SOME aircraft, it shouldn't be checked on ANY?

Not at all, if it is your thing to check it go for your life but dont criticise people who don't do it or who don't see the value in it.

If it was a safety critical issue it would be in the manufacturer's documentation.

It isn't so it is clearly something that someone (not the manufacturer) has decided is a good idea. It may well be a good idea, but if the manufacturer, who has some experience in cold weather operations, doesn't think it is of such critical importance, then perhaps it is a nice to do not a must do.

I have never done it on any of the jet types I have flown, never seen any suggestions to do it, and I have flown across Europe, North America and Asia. Doesn't mean I know it all, but never seen it mentioned.

Things tend to take on a life of their own and become "safety critical" when in fact they are just the product of someone deciding that they reckon it is a good idea. All of a sudden if you don't do it, you don't know what you are doing "because even cadets know to check...."

Our company (Airbus) walkaround video shows the chap physically rotating the fan blades with the audio stating to check that the blades are ice free and rotating freely, although it doesn't spell out in the FCOM as to 'how' you check the fan, just that it should be checked.

Snakecharma, your assessment does make a lot of sense, even if it's somehow made its way into one of our company videos!

I admit I have not looked at a 320 fcom as I have not flown a 320 so my brave pronouncement may well be just that, brave! Nevertheless I have not seen it in the 737, 777, 330, and sundry smaller jets. Doesn't mean it isn't there just not seen it.

I tend to pay as much or more attention to the back of the engine as I can see the back of the fan blades and into the back of the engine,where looking in through the front isn't as easy.

All I was getting at is that this "procedure" isn't as universally accepted as perhaps some think and don't look down on those that don't accept it as a gospel truth.

Walk arround or run arround.
 

I have found a few interesting things on walk arrounds that i am glad that i did not take of with.
We should start a new thread and see who has the best, worst story.
Nevermind.
The question was about the 787-800 and its thrusted CFM 56. ( What does CFM stand for by the way, and yes i do know, but do you. Ardwarg is at the core of the answer if i am not mistaken.)
1
Birds, any small feathers stuck to the fan indicates a birdstrike, and if on the inner part , has gone into the core.
This you can not see from the back, and also you can better see the core statorvans .

2
The 800 is very low and sucks gravel like a ......... Hoover.
I rotate the fan and look for damage to the leading edge,, etc.

Lastly, why in the name of Odin would i fly this bastard aircraft, born the same year as me , WITHOUT giving the two good engines a good check/look
when i CAN!!??
Oh , and i still have all my fingers, done to much carpentry to put them in rotating things.

By the way centermounted engines never suck gravel and birds.
The new thing is that we are going to start using common sence ,
I dont depart for a 6hr flight with a 78 ton A/C and 26k thrust and just give the engines glance : Cause they sounded fine on the way up here!!??

Anyway,
How do you get ride of ice on the fan if there is any?
You may find the answer counter intuitive.

Next thread
Why does he kick the tire?

Cpt B

Depends on how/when it got there

If it was inflight the signatures are vibration and there are published procedures for spooling up the engine to centrifuge it 0ff.

If it is there in walk-arrounds then call a mechanic and he may remove it with a heat source.

Just remember that if you use spoolups, they have to be high enough to actually dislodge the ice and they have to be often enough that the shed itself is small and won't damage the engine when it bounces off the cases

How Engineering Works
 

Harmless tests with a vague purpose are often deemed pointless, don't do it...

...right up until that one occasion where a significant problem is found because someone was doing it anyway.

Besides, I don't think anyone with an ounce of mechanical sympathy would ever tire of setting in motion such a great hunk of metal that's so nicely made and turns so smoothly.

I can remember seeing a Cathy pilot, a few decades ago in Taipei, doing just this prior to our onwards leg to HK. Not that we'd noticed but apparently something feathered had gone into No.2 (747-200 I recall) on departure from Fukuoka (or approach to Taipei), and we weren't going anywhere until he was satisfied that all was basically well.

There is a big difference between 'it's not necessary to do that." & "Do not do that." In the former it is your choice if you want to spend time, cover your back-side, have fun, feel superior etc. etc. In the latter....clear & simple.
For AB guy; it would seem odd to have an FCOM/video telling you to hand spin the engine on an AB and not to do so on the very same engine on a B737. Surely it is an engine thing not an aeroplane thing.
I was taught to do it on PW JT-8's, first flight of the day, especially in winter. It could have been sitting out there for a few days in freezing conditions. And why not? 2 secs of hands on and bonding with your engines. Give the spinner cone a kiss if you can reach it. Hug the radar dome on a TS day: whatever floats your boat. None of it is a "Do Not."

For the engine spinners: do you do it forwards or backwards? Let's get to the important nub of the matter. ;)

Do I read this right, as an engineer you discourage spinning the fan on a turnaround?

I am with RAT5, I may do it on a first flight after a cold night or when ice can be suspected. Not as the norm on any turnaround just because I can..

Remove ice on CFM 56 on turnaround.
 

Ice picked up on approach and or taxi in is often easy to remove the following way. And Yes you may look like a nutty Cpt but it works:
Do the tecklog, get Jr to do the setup and jump out before the engines cool down.
Spin the fan counter clockwise after finding ice on the backside of the blade.
So backwards of normal spin, this draws hot air forward and starts melting the ice. Remember to do both alternatley and fairly fast.
Then remove all slush and check all 24 before blasting of to warmer destination.
This can save You delay , when slots are hot and temp is not!
Has worked from +1 down to -10 for me.
If airport is good they have plenty heaters, but why bother when you can do it yourself. You have a slot arrived 7 min early on a standard 25 min turnarround.
Cabin need waste and water, a few lift offs, at remote parking , with bussed Pax, and remoter deice if needed on a friday afternoon two sectors and a 12hrs duty day. And a slight case of homengitis Catastroficus and 5 hrs of sleep on day 5.
Hey, lets turn this moneymaker in the right direction.
SAFELY .

Gone Fishing
Cpt B

Good tip. Does it remove all the ice? I'm just wondering how it melts the ice on the fan outer edges.
Can't see this working on the bigger fans but its worth a go I suppose when no heaters are available.

amazing! of all the engines I have spun backwards on a turn-around at the gate I have never felt the warm air on my fingers.

I wonder what Barit 1 and TD have to say about this ?