Enstrom Corner
Join Date: Feb 2014
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Grip Friction
Hello there, I am new at this forum but it seems like there is a shortage of experienced Enstrom mechanics around for the enstrom lovers out there. As an enstrom AME, I have to say that most importantly, maintenance action to prevent ground rocking is to re-introduce factory grip friction about the flapping and lead-lag axis. That will control the blades and tracking will become predictable and efficient. The age old adjusting of the oleos is important but is more of a bandaid in my opinion because we don't always have the luxury of a flat landing area with just the right amount of friction for the skids to slide on.
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Ground Control
Just my 2 cents. It seem that you are going to great lengths to get this ship right, just remember to have your grip friction right, this will keep the machine stable in any condition and will allow you to ground track and flight track with comfort
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Yep lack of mechanics that know the quirks of the Enstrom is a problem. If you read earlier the previous owner got duped by one around here. Leaves me with noone. My mechanic and I will have to learn to do it ourselves. I plan on attending the factory training, but seems that focuses on the 480 more than piston. I guess all is the same or similar, but this is a 70s vintage bird. I hope the maintenance manual will help with the grip friction or I can get up and see the previous mechanic that rebuilt this in the past.
Last edited by lvflyer; 16th Mar 2015 at 23:01.
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TRACK & BALANCE
They have a real good procedure in the maintenance manual starting with using trim tab adjustments for removing stick shake-but you have to have a stable A/C on the ground firstly. That's wy friction is so impotant. I have been to the enstrom course with Lee Berdue I guess he forgot to mention this procedure, had to figure it out on my own. Different size shims (.001 thou on up to .020 I believe)can be purchased(cheap to get) combinations of these shims are fitted behind the DU washers to get the proper grip close tolerance fit, then when you start clamping the grip it will have a nice friction to it. Rule of thumb would be the grip should just remain in the full flapping position while blades are off. I can walk you through all the steps if you like and chances are, you probably won't need a stobex .Good luck with it all.
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I did fairly extensive testing of the Dynavibe on the Enstrom helicopters and it works just fine. it is slightly slower than a Chadwick but is easy to use and accurate. I made a polar chart for it if you are interested.
[email protected]
[email protected]
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We don't recommend setting the flapping shims with tight friction anymore, as the friction changes the track will change. We actually shim the flapping bearings inside the U block now and don't worry about the friction at all.
In my extensive experience tracking Enstroms, I found that the best procedure is to leave the shimming loose enough that the grips do not stay up. Our latest tracking procedures (which I wrote) can be found on the web site under; Support : Technical Support : Tech Tips.
Also there is a revised TR balance procedure. Placing the accelerometer horizontally takes most of the hassle out of the balance procedure.
In my extensive experience tracking Enstroms, I found that the best procedure is to leave the shimming loose enough that the grips do not stay up. Our latest tracking procedures (which I wrote) can be found on the web site under; Support : Technical Support : Tech Tips.
Also there is a revised TR balance procedure. Placing the accelerometer horizontally takes most of the hassle out of the balance procedure.
Join Date: Nov 2001
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A few thoughts on tracking.
The new tracking tips are an improvement as is the advice on shimming the grips. Our experience of easing the grip friction so they drop under their own weight is it makes the whole tracking procedure easier and the ship fly smoother. We've been doing that for years now.
Some years ago I made a Laptop based track/balancer. Main rotor only. It uses a couple of modules with accelerometers in 3 planes and fires a strobe. I've used it successfully on quite a few ships over the years.
I have often noticed a problem with old/assorted/repaired/repainted blades. (plenty of them in the UK!)
It is most obvious at the hover stage. Once the hover is set to 0.2 ips (or less), if the tip targets are strobed they are usually tracking nearly in the same plane. If the aircraft is then landed and the tip path observed with no pitch applied at the same RRPM, a well matched set will be still tracking the same. The rest of the procedure is easy and the ship will fly well.
However, I have seen several times big deviations at flat pitch with tip path splits of 3 or 4 inches, yet close tracked in the hover. These blades are almost impossible to track. They either fly well in the cruise and are horrible in autorotation or are a lumpy compromise in all phases of flight - and it takes hours to get it that 'good'.
I'm sure on new ships the blades are right but it seems 'it' goes out as blades age, get painted and get swapped over the years.
The 'it' is chordwise centre of gravity.
By matching the chordwise c of g of all 3 blades, it is possible to correct this problem and get the ship to fly smoothly, easily. It can be done with paint (in theory), by substituting a blade or by redistributing weights at the blade tip ( I know,
) My first aircraft had 2 'A' blades and 1 'U' and it was a pig when I got it, but once set up it flew beautifully until one of the A's started to debond. With a smooth flying ship a 2.5 inch trailing edge debond was immediately obvious although not alarming. I scrapped the blade.
My second ship had a set with consecutive numbered blades but was bad. Again with a little effort matching chordwise c of g, we got it silky smooth.
I suspect if the chordwise C of G is way out, the blade is getting towards end of life and should be carefully watched for debonds, or scrapped.
I'm certain that a mismatched set makes for a poor ride and hours spent tracking.
I picked up a set with consecutive numbers and only 260 hours TT to replace my odd set so I'll be interested to see how they fly when my 28 takes to the air again in just a few weeks.
Some years ago I made a Laptop based track/balancer. Main rotor only. It uses a couple of modules with accelerometers in 3 planes and fires a strobe. I've used it successfully on quite a few ships over the years.
I have often noticed a problem with old/assorted/repaired/repainted blades. (plenty of them in the UK!)
It is most obvious at the hover stage. Once the hover is set to 0.2 ips (or less), if the tip targets are strobed they are usually tracking nearly in the same plane. If the aircraft is then landed and the tip path observed with no pitch applied at the same RRPM, a well matched set will be still tracking the same. The rest of the procedure is easy and the ship will fly well.
However, I have seen several times big deviations at flat pitch with tip path splits of 3 or 4 inches, yet close tracked in the hover. These blades are almost impossible to track. They either fly well in the cruise and are horrible in autorotation or are a lumpy compromise in all phases of flight - and it takes hours to get it that 'good'.
I'm sure on new ships the blades are right but it seems 'it' goes out as blades age, get painted and get swapped over the years.
The 'it' is chordwise centre of gravity.
By matching the chordwise c of g of all 3 blades, it is possible to correct this problem and get the ship to fly smoothly, easily. It can be done with paint (in theory), by substituting a blade or by redistributing weights at the blade tip ( I know,
) My first aircraft had 2 'A' blades and 1 'U' and it was a pig when I got it, but once set up it flew beautifully until one of the A's started to debond. With a smooth flying ship a 2.5 inch trailing edge debond was immediately obvious although not alarming. I scrapped the blade. My second ship had a set with consecutive numbered blades but was bad. Again with a little effort matching chordwise c of g, we got it silky smooth.
I suspect if the chordwise C of G is way out, the blade is getting towards end of life and should be carefully watched for debonds, or scrapped.
I'm certain that a mismatched set makes for a poor ride and hours spent tracking.
I picked up a set with consecutive numbers and only 260 hours TT to replace my odd set so I'll be interested to see how they fly when my 28 takes to the air again in just a few weeks.
Last edited by Gaseous; 11th Feb 2014 at 02:08.
Hey Enstrom community!
Our flight school just sold our Schweizer 300C due to parts (un)availability and we are days away from getting an Enstrom 280FX. A lot of training material will need to be established and I'm looking for a helping hand.
Are any flight manuals or training manuals that you could share in pdf format?
I got some great material for Enstrom 480 that I could share, but we aimed slightly lower than our initial expectations.
Any help would be greatly appreciated,
Jure
blenderpilot(at)gmail.com
Our flight school just sold our Schweizer 300C due to parts (un)availability and we are days away from getting an Enstrom 280FX. A lot of training material will need to be established and I'm looking for a helping hand.
Are any flight manuals or training manuals that you could share in pdf format?
I got some great material for Enstrom 480 that I could share, but we aimed slightly lower than our initial expectations.
Any help would be greatly appreciated,
Jure
blenderpilot(at)gmail.com
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Join Date: Mar 2008
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RFM
I have never seen a PDF version of an EN28 RFM but that Pilots Training Guide is a great place to start. I do have a scanned version of a 480B RFM, and PDF versions of the EN28 IPC and Mx manuals. Let me know if interested.
-JMc
-JMc
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PDF
I have PDF versions of the 280fx/f28f and 480B Pilot Training Guides and the 480B RFM. PM or email [email protected] if you need.
-JMc
-JMc
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Dupont have you heard or seen the PB-3 system? It uses a smart phone app for the computations so all the expense of software and processing is gone. Here is what the manufacturer sent me when asked if it could be used on an Enstrom.
> Is the PB-3 OK to use with an Enstrom 280C? Can you refer me to any
> user that has experience using this with an Enstrom or other 3 blade
> helicopter? Where do I buy in the states? I was considering a
> Dynavibe till I read about this.
Sorry, because the rotor balancing capability of the PB-3 is very new,
I only know about its use with 2 bladed gyro rotors. A couple of
customers have started using it with helicopters but I haven't had any
feedback from them yet.
As far as the PB-3 is concerned, I can't see any reason why it can't be
used to balance a 3 bladed rotor. It should still be able to measure
the vibration phase and magnitude. The real unknown is whether the PB-3
app's support for move lines is adequate for that application. At this
time, the app only supports 2 move lines. Mind you, that's better than
what the Dynavibe supports because that product doesn't make any
attempt whatsoever to suggest adjustments. I expect in the future the
app will be extended to make it more useful for helicopter rotor
balancing.
At the end of the day, you could still use the PB-3 to measure the
vibration values and then plot them manually on a paper polar chart that
shows the move lines that have been determined by the helicopter's
manufacturer. That's all the Dynavibe can do, anyway.
Worldwide sales of the PB-3 are direct from Smart Avionics. The
prop+rotor version of the PB-3 costs 650 UKP and UPS shipping to the USA
is 60 UKP. Payment is by PayPal or bank transfer. Current lead time is
less than 1 week.
> Is the PB-3 OK to use with an Enstrom 280C? Can you refer me to any
> user that has experience using this with an Enstrom or other 3 blade
> helicopter? Where do I buy in the states? I was considering a
> Dynavibe till I read about this.
Sorry, because the rotor balancing capability of the PB-3 is very new,
I only know about its use with 2 bladed gyro rotors. A couple of
customers have started using it with helicopters but I haven't had any
feedback from them yet.
As far as the PB-3 is concerned, I can't see any reason why it can't be
used to balance a 3 bladed rotor. It should still be able to measure
the vibration phase and magnitude. The real unknown is whether the PB-3
app's support for move lines is adequate for that application. At this
time, the app only supports 2 move lines. Mind you, that's better than
what the Dynavibe supports because that product doesn't make any
attempt whatsoever to suggest adjustments. I expect in the future the
app will be extended to make it more useful for helicopter rotor
balancing.
At the end of the day, you could still use the PB-3 to measure the
vibration values and then plot them manually on a paper polar chart that
shows the move lines that have been determined by the helicopter's
manufacturer. That's all the Dynavibe can do, anyway.
Worldwide sales of the PB-3 are direct from Smart Avionics. The
prop+rotor version of the PB-3 costs 650 UKP and UPS shipping to the USA
is 60 UKP. Payment is by PayPal or bank transfer. Current lead time is
less than 1 week.
Join Date: Jul 2000
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Just saw the new trainer yesterday at HeliExpo. Called the TH180. Looks interesting. They trimmed the tail some and lowered the empty weight. They are shooting for around 1500 pounds. Personally I don't feel the lowered enough. The engine is a Lycoming HIO-390 producing 210hp. Non turbo charged. I think that Enstrom will lose some of the training market they already have the operators in the higher elevation. The rotor head is the same, too bad they didn't go with the elastameric dampers. The reason I was given that hydraulic dampers are better at preventing ground resonance.
They added a governor and electric clutch. I understand the governor, but the electric clutch? The old system works extremely well and has almost no maintenance except for a possible adjustment or two during inspections.
It will be interesting to see how it goes over in the next year or two.
The machine on the floor is a mockup as the only real machine right now is an engineering test machine.
They added a governor and electric clutch. I understand the governor, but the electric clutch? The old system works extremely well and has almost no maintenance except for a possible adjustment or two during inspections.
It will be interesting to see how it goes over in the next year or two.
The machine on the floor is a mockup as the only real machine right now is an engineering test machine.
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I think its a big mistake sticking with a big old piston engine considering price of Avgas in Europe plus they are thinking of making some changes to Avgas for environment etc
and as you say the elastomeric dampers were great just sacrificed for to save other changes.
and as you say the elastomeric dampers were great just sacrificed for to save other changes.
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Since their primary market is still the USA, they most likely decide to go the piston route. Also they already have a turbine trainer the 480. As for the elastomeric damper, Enstrom admits that they are basing the machine off the current type certificate, so they are very likely stuck with the hydraulic dampers.
