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Bell 412

Old 13th Aug 2005, 19:51
  #101 (permalink)  
 
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So to resume:

1- The 412 has the possibility of ground resonance as any other helo with lead-lag movement in the blades.In the first post I was looking for a previous incident without luck.

2- The replies derived to the 412 well known Ground Bouncing capability

3- Nick:
2) It takes something mis-adjusted or mis-maintained to get it, because all helos that have lag hinges have systems to quell it. Manufacturers have to prove they are immune to ground resonance to themselves and to the FAA. Those systems (oleos, dampers on skids, dampers on blades, elastomers on all the previous) do not cause ground resonance, they prevent it.
This is something... I was missing, I was thinking that a blade with a bad lead-lag damper will develop the ground resonance, but not, it's there just to preven it, Thanks.

Best regards.
Aser
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Old 15th Aug 2005, 09:52
  #102 (permalink)  
 
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I agree that generally with the 412 we are talking bounce which is not resonance. Both cyclic position, and to a larger degree some addition of collective will help. We have found the bounce can become quite a thump particulary on wooden wellheads, where some movement of the deck allows the situation to worsen. In cases like these pilots do tend to hold the collective tightly and while they bounce, unconciously bounce the collective as well increasing the effect. I personally have not heard of this developing into resonance as such, but it does get your attention for sure. Some good technical feedback on this has come thru, Thanks guys.
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Old 15th Aug 2005, 21:16
  #103 (permalink)  
 
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Many of the 412's I have gound run have been prone to some form of bouncing. It has always happened on concrete and starts at about 95%+ with min pitch. Invariably the aircraft has been lightly loaded (empty actually). Certainly there was the thought that this could develop into full ground reasonance if it were allowed to continue Raising the collective slightly seems to be the cure. It was very uncomfortable and I am not able to say whether the condition is divergent, or not.

I have never experienced this problem on either a B212 or a B205 although I have experienced collective bounce on a B205. The situation there was a gentle run on on a bank of shells/stones caused by insufficient friction on the collective.

Hope this helps.

NC43
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Old 18th Aug 2005, 19:26
  #104 (permalink)  
goaround7
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412 operating costs

Hi guys,

I've got the manufacturer's and 'blue book' type costs but can a couple of you give me some real world gen on operating costs for 212/412 in harsh(ish) desert environment but with hangar and daily maintenance available doing pax and equipment transfer with one to two hour flights, 100 hours a month - minimal sling, no high cycles, nothing unusual ?

Eg. real maintenance, unplanned spares, fuel, oil, blades etc.

Thanks,

G7
 
Old 19th Aug 2005, 19:45
  #105 (permalink)  
 
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Go with Conklin and D's estimates and you will do more than well, the 412/212 has no surprises.

The desert should not pose any problem for the 212/412 its one of the most dependable aircraft this world and its surroundings have available for you to make money with it.
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Old 19th Aug 2005, 21:19
  #106 (permalink)  
goaround7
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Thanks, we got those.

Recent newsletter reckons US$ 606 per hour for 412 then ?
 
Old 29th Aug 2005, 20:35
  #107 (permalink)  
 
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Came to this somewhat late, but why not jump in anyway!

IME the 412 ground bounce is usually caused by track/balance problems, and can't always be eliminated no matter how long you try. I've seen it caused by a t/r imbalance. We worked on the m/r track/balance for weeks, with no success in lowering the ground bounce. Then when the t/r balance was done as part of the scheduled maintenance, it was found to be well out of tolerance, and when balanced the ground bounce was gone.

It's a miracle when a 412 has no vibrations anyway, considering that it starts out with the blades in different planes. Sometimes you just have to live with a ground bounce, but I try to get it tracked out. Raising the collective slightly usually helps, as already mentioned.
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Old 19th Sep 2005, 22:25
  #108 (permalink)  
 
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412 Ep Hp Sp

What is the difference in performance and structure between these 412 versions? Is there any other that i might not know about?

J
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Old 19th Sep 2005, 22:57
  #109 (permalink)  
 
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How much time have you got :-)
Engines are different across the 3 models, although engine models are sometimes common between SP/HP (-3BE/BF/BG), and between HP/EP (-3D). SP uses 212 tail rotor driveshafts with driveshaft clamps. HP/EP uses Thomas Couplings on the tailrotor driveshafts. HP/EP have ITT trim for Engine #2, SP has the 212 setup. EP has different Damper Bridges on the Main Rotor Head, but I think this can be retrofitted back to HP/SP. EP cannot fly with older style Damper Bridges though. EP measures rotor torque at the Main Rotor Shaft output to the Main Rotor Head. SP measure at the MGB input from the engines. Structurally, from memory, they are the same. Components are upgraded for each successive model, and engine horsepower increases with each model to hide the fact that the later models are heavier :-)
As far as perfomance goes, you'd have to speak to a driver.

noooby
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Old 20th Sep 2005, 01:27
  #110 (permalink)  
 
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Quite right except both the HP and EP have mast torque wich uses mast twist to determine torque with a lot more accuracy than the "No P" and SP wich totalize the torquemeter from eng #1 & #2 as on the Bell 212.

The "412 No P" or "412 Straight" or "412 Classic" how ever you want to call it, is structurally very close to the Bell 212 not having the aft center fuel cell (five fuel cells in lieu of 10).
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Old 20th Sep 2005, 08:05
  #111 (permalink)  
 
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Does anyone care to discuss the fuel system and how it works?
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Old 20th Sep 2005, 10:36
  #112 (permalink)  
 
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Yes, the Bell fuel system!!
Well it's not that bad ,to start with the 412 Classic is basically the same as the 205 and 212 fuel system with 5 main tanks giving approx 1450lbs fuel.
The 412 SP/HP/EP, has a ten tank system 6 floor tanks, with fwd, centre and aft floor tanks on each side, the centre and aft tanks take the same space as the 2 floor tanks in the 205 /212/ 412Classic with the fwd tanks fitting into the floor cavity behind the pilots seats.
3 of the 4 aft tanks are the same as the 205 /212/ 412 Classic with the extra tank befind situated in the rear hellhole area. With the fuel system extended fwd and rear in the airframe longitudinal CofG became a problem , so Bell came up with a series of stand pipes and valves to keep the CofG move to a minimum (a total move of approx 4 ". between 136.0 -140.0)
To do this Bell do it in a series of 6 "Burns"
Burn 1 is approx the top 1/4 of the 4 rear tank as the flow into the floor tanks
Burn 2 is the centre floor tank on each
Burn 3 the next 1/4 of the aft 4 tanks
Burn 4 is the fwd floor tank on each side (approx 800lbs left at end of burn 4)
Burn 5 last 1/2 (rest) of 4 aft tanks
Burn 6 remaining fuel in aft floor tanks.
Hope that helps and isn't too confusing, it had me stuffed to when i first did the course!!

Oh yeah and the main reason for the fuel system change?
More fuel Classic 1450lbs approx 225 nm
SP/HP/EP 2150lbs approx 350nm
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Old 20th Sep 2005, 19:50
  #113 (permalink)  
 
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Simple really!!!! Until the underfloor Jet Pump clogs or fails and you find that you can't get fuel out of the center underfloor tank!! DOH!! Stoopid stoopid stooopid system. But hey, that's the price you pay for continually modifying a UH-1!!!
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Old 20th Sep 2005, 22:19
  #114 (permalink)  
 
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Its not that bad the fwd floor tanks on each side and centre floor tanks on each side are conected together by the standpipe interconect to maintain even fuel on each side and you have the interconnect valve on the rear floor tanks and crossfeed after the pumps so you can still get justabout all your fuel if a jetpump or boost pump fail !
If you want to see a sh1t fuel system just look at the Super Puma ,7 tanks, no direct crossfeed to the engines and only a mickey mouse "crossfeed" pump between tanks if it fails and the crew don't monitor the fuel levels between sides you have the potential of running fuel out on one engine and still having heaps to the other engine , this has disastrous potential if you are running a long range internal tank as it only feeds into one side!! not so in a Bell!
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Old 21st Sep 2005, 16:08
  #115 (permalink)  
 
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Thanks guys. Only one info is puzzeling me. What does SP/HP/EP stand for exactly? The more i ask, the more different explanations i get
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Old 21st Sep 2005, 21:52
  #116 (permalink)  
 
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SP-Special Performance
HP-High Performance
EP-Extra Performance
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Old 21st Sep 2005, 22:11
  #117 (permalink)  
 
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In my Flight Safety manual it shows the following infor:

PT6T-3B PT6T-3D
100%Torque Twin engine torque limit

1800 SHP !800 SHP

Continuous Twin engine Torque limit

1600 SHP 1600 SHP

Continuous OEI Torque Limit

970 SHP 970 SHP
765 C ITT 820 C ITT

30 minute OEI ITT Limit

970 SHP none
822 C ITT
2.5 minute OEI ITT LIMIT

1025 SHP 1100 SHP
850 C ITT 925 C ITT


Hope this helps
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Old 22nd Sep 2005, 05:05
  #118 (permalink)  
 
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Thank you all. That should do it.
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Old 22nd Sep 2005, 21:21
  #119 (permalink)  
 
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Not that its important, but I think the correct designation for EP is Enhanced performance.
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Old 7th Nov 2005, 09:28
  #120 (permalink)  
 
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NSW Police to purchase 412's

Any truth that the NSW Police are going to purchase 412's to replace their aging AStar fleet

Last edited by Induced Drag; 7th Nov 2005 at 11:44.
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