ATR72-500 Prop Vibs

[Teki_ATR72]

Has anyone experienced vibrations (prop generated) through the aircraft on descend through about 6000' at 240kts, with little or no TQ?

Keen to hear how the problem was fixed. :(

[Miserlou]

Never heard of it with that type. It's a good bit of kit, the 75.

Had a 42-300 with a similar problem of props not quite balanced properly which made the a/c shake it's tail occasionally. It was like the aircraft had a shiver up it's spine!

I take it it's your terrain which requires steep descents?

Have you tried Power Management to MCT to see if the frequency changes with the increased prop RPM?

[Teki_ATR72]

These vibs happened during normal descent prolife. 3 degrees.
:(

[Miserlou]

I tried, last night, to see if I could feel or hear anything which you describe, and tried MCT too.

Nothing unusual.

Still sounds like the props need balancing.

Do you have any acronyms for ATR?
I've only got , A Tad Ropey and Aeroplane, Terreibly Rong!

Why, when you spend x million dollars on a new a/c do they forget to put a squelch on the audio panel and use Citroen seats?

What are your biggest nigs about it?

[HugMonster]

The seats without the adjustable thigh support I'll agree with you. Put that back on, and the seats aren't much worse than most aircraft seats I've encountered.

The squelch is rarely installed on the audio panel. You'll find it on each VHF Comm box if you look. :}

I and quite a few friends have flown ATR and similar (equivalent) turboprops. The general concensus (but not unanimous) opinion appears to be that the ATR beats most of the competition hands down, including F50, Dash-8, all models, etc. etc.

I agree with that assessment - far quieter than most, less vibration, good ergonomics on the flightdeck (except for the draught on the kidneys from the docs flap), good visibility, easy handling, very forgiving (yes, even in icing conditions if you follow the recommended procedures - Indiana newspapers please copy) and very roomy cabin. I like the H-mode (hate not having an APU) and the only thing that got me was the tailprop.

[zerozero]

Is the vibration on one particular aircraft or all of the ones you fly?

I ask because I once flew a Caravan off of gravel strips. Naturally, every now and then, the prop needed to be dressed.

Over time I started to detect a vibration at reduced power settings when I was entering the traffic pattern.

I told the mechanics about it and they said they balanced the prop. After that the vibration lessened somewhat but still existed.

A couple days later the plane is grounded due to the fact the mechanics were using the wrong template over the blades to determine whether or not its wear was within limits.

As you may know the Caravan may be equipped with an aluminum or composite propeller--different shape--different template--different tolerances.

[Miserlou]

Huggie,

Not always easy to convey true sentiment. My complaints were only in relation to ATRs, not relative to other types.
We have 4 different models, 2 of 42 and 2 of 72 all with different quirks and foibles!

The squelch I mean is for the intercom or voice activation. Even spam-cans have those!

I know its probably the best little airlliner around.

And for good measure, my favourite ATR thing is the cross-wind limit!

[Teki_ATR72]

Yes, we have done the prop balancing thing but it hasn't stopped this particiular type of vibration. Normal prop imbalance can be felt through the control column and is during all phrases of flight.
The vibration I'm speaking of seems to start at lower altitudes and only at high IAS, like 238 to 250kts with normally little or no TQ. In fact the other day I was flying another aircraft in the fleet, where the vibiration started at 240kts with 36-40% TQ. The vibrations were felt all through the aircraft. By advancing the PL slightly, the (inc TQ) the vibration disappears. So don't believe this issue is one of balance.
Any more thoughts?:confused:

[wandrinabout]

Teki
Had a similar scenario to yours for a while, although it wasn't tied to TQ settings, just high speeds at lower density alts.
It was one of the banana seals for the flap tracks on the wing/fuse fairing, it was almost non existent. Airflow getting into the big box and buffeting around. The noise/vib was more pronounced mid cabin in this case.
Have also had those clear prop leading edge tapes being partially peeling off, causing a bit of fluttering/noise at certain speed/power combos. Nothing siignificant though.

Miserlou
My pet hates - the constant rudder trimming required, esp single engine, and that bloody alt select knob - why didn't they put a detent for every 100ft like most others do? And of course the poor mans APU

[Brakes...beer]

Not sure if this is your problem, Teki, but a while back I was in the RHS of one of our 72-210s for a couple of air tests trying to find out what was causing intermittent sharp yawing. It felt like one or two small rudder inputs at low altitudes and high speeds. We thought it might have been a problem with the yaw damper.

Of course, it's generally at low altitudes and high speeds that you have the PLs right back. The No1 engine was momentarily going into low pitch; the LO PITCH light would flicker on briefly, at the same time as the yawing, but there'd be no other indication. Watch the LO PITCH light when you bring the PLs to idle and that might reveal the problem, if that's what it is.