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AS350 Astar/Squirrel

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AS350 Astar/Squirrel

Old 28th Nov 2019, 14:44
  #821 (permalink)  
 
Join Date: Mar 2019
Location: Europe
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Originally Posted by JimEli View Post
To my knowledge, I don’t believe the ‘+’ was ever adopted as the official nomenclator, at least never in the US. The RFMs simply refer to the variants as “AS 350 B3 Arriel 2B” and “AS 350 B3 Arriel 2B1”. The current model designation is “H125”, however the RFM is still entitled “AS 350 B3e”. IMHO, in the US, the manufacturer has always clouded the differences to the point of it ostensibly being a contributing factor in several accidents.
Curious to read about the accidents you're referring to?

Here in Europe it's very clear;
If you look at the EASA Type Rating list, it uses the following names for each variant:
-AS 350 B3) - Ecureuil
-AS 350 B3 Arriel 2B1) - Ecureuil
-AS 350 B3e) - Ecureuil

The B3 Arriel 2B1 (a.k.a. B3+ for short) and B3e only require familiarisation training between them, the B3 requires differences training. If someone simply uses "B3", I think it's safe to assume they mean "B3".

P.s. I believe the "B3+" may have come from Airbus initially (similar to their use of + for EC135's). Even if it's not official, it is clear which variant it refers to and is shorter than writing "...Arriel 2B1" every time.
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Old 29th Nov 2019, 02:57
  #822 (permalink)  
 
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Originally Posted by ApolloHeli View Post
Curious to read about the accidents you're referring to?

Here in Europe it's very clear;
If you look at the EASA Type Rating list, it uses the following names for each variant:
-AS 350 B3) - Ecureuil
-AS 350 B3 Arriel 2B1) - Ecureuil
-AS 350 B3e) - Ecureuil

The B3 Arriel 2B1 (a.k.a. B3+ for short) and B3e only require familiarisation training between them, the B3 requires differences training. If someone simply uses "B3", I think it's safe to assume they mean "B3".

P.s. I believe the "B3+" may have come from Airbus initially (similar to their use of + for EC135's). Even if it's not official, it is clear which variant it refers to and is shorter than writing "...Arriel 2B1" every time.
Are you aware the factory training manual refers to the AS 350 B3 Arriel 2B as the "B3 Mod"?

As for the accidents, here's a start:

All three B3 variants incorporate a FADEC and an identical red GOV caution light. The light, requires similar but different responses in the 2B1 and 2D, but completely different in the 2B variant. In the 2B, the pilot must manually control engine RPM via a twist grip after the red GOV light illuminates. The 2B was initially produced with a red mechanical “slider” lever used to unlock the throttle range above the flight detent. After numerous incidents involving misunderstanding/misuse, the manufacturer removed the slider and replaced it with an electrical solenoid that automatically allowed access to the increased range. However, the solenoid was unreliable, subject to seizing and demonstrated to the factory to overheat and fail after a very short period of time. The solenoid mechanism went through another re-design to address these additional issues. A resulting alert service bulletin imposed preflight requirements and limitations upon the aircraft. Throughout this process, a bewildering array of conditional revisions to the flight manual and emergency service bulletins, all which required cross-referencing created confusion among operators and pilots, many of which were never aware of them. The manufacturer has a habit of addressing design flaws via procedural changes (examine the dual hydraulic option to unravel another human-factors nightmare). Here are a few accidents (in no specific order) related to 2B manual governor operations from which you can draw your own conclusions:

Report #1
Report #2
Report #3
Report #4
Report #5
Report #6

Last edited by JimEli; 7th Dec 2019 at 15:27. Reason: added add'l report
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Old 29th Nov 2019, 19:11
  #823 (permalink)  
 
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Originally Posted by ApolloHeli View Post
Curious to read about the accidents you're referring to?
...
Continuing the accident discussion you inquire about...

Historically, the manufacturer has a pattern of generating incomplete solutions for correcting flawed systems. How long did it take the factory to incorporate a simple guard over the ACCU TEST switch to prevent inadvertent activation? The ACCU TEST switch removes stored hydraulic pressure in the tail rotor yaw-compensator, significantly increasing the forces required to move the pedals. Incidentally, in many aircraft the ACCU TEST switch is adjacent or very near the landing/taxi light switches. And for years, the ACCU TEST switch was referred to as HYD TEST, which probably contributed to operator confusion. The manufacturer used both labels throughout the flight manual for many years.

See this accident report, and this report.

When the factory started to offer a dual-hydraulic option, it continued to obscure switch labels, compounding the confusion. The dual version removed the 3 accumulators on the main rotor servos, yet retained the yaw-load compensator in the tail. Thus, the function of the ACCU TEST switch was altered, but to this day, it retains the ambiguous label.

At the same time, the HYD CUTOFF (“yaw servo hydraulic switch, is also called the hydraulic pressure switch or hydraulic cut off switch in various Airbus Helicopters rotorcraft flight manuals” – FAA’s statement) switch on the collective head also changed function since it was now impossible to actually “turn off” the hydraulics. Further contributing to the confusion, is that the physical switch and their locations are identical to the single-hydraulic version.

In addition, the RFM was (and still is) written from the perspective of a single-hydraulic configuration. All of the dual-hydraulic information is contained in a brief supplemental chapter inserted into the back of the RFM. The supplement highlights changes to the operating procedures which must be incorporated into the manual’s runup, shut down and emergency procedures. Imagine flying NVGs on an EMS flight and asking the nurse, an FAA required crew member for off-airport NVG landings (?) to find the dual-hydraulic emergency procedure so you could review it?

Next followed a series of incidents/accidents in which it was believed pilots made procedural failures, by attempting takeoff with incorrect switch positions. These inappropriate switch configurations, and resultant loss of control were never alluded to in the RFM. Further exacerbating these flaws was the fact that the cockpit lacked a warning indication of the potentially grave misconfiguration.

See this accident report, and this report the author is aware of additional related incidents which didn’t result in the creation of an NTSB report.

What followed next, was a failed attempt to address the design short-comings by publishing a series of communiques describing the functions of the dual-hydraulic system and the inadequate established procedures for preventing incorrect switch configuration. The result was the somewhat predictable, yet horrific accident at Frisco, Colorado.

See this accident report.

Oddly, the immediate response to this accident was to change the runup and shutdown procedures via an emergency service bulletin. The altered procedures mandated a confusing series of page swaps to the RFM, which had the pilot now perform the runup check during shutdown. This has the extremely odd and useless consequence of performing a check of a critical system after the flight is completed. Subsequent revisions to the manual left operators confused as to it's proper arrangement. A follow-on “pen and ink” change to the RFM included the addition of the almost laughable statement, “The yaw servo hydraulic switch (collective switch) must be in the “ON” (forward) position before takeoff.” A command to a pilot which seemingly forbids him/her from making a switch configuration mistake!

The factory then modified the warning system to alert the pilot of misconfigured switches. However, the modification was only installed on new aircraft and offered for optional purchase to install on existing aircraft. The manufacturer finally designed a new mono-stable ACCU TEST switch which would prevent the incorrect switch configuration, and thus the heartbreaking saga of a human-factors nightmare is closed.

Last edited by JimEli; 7th Dec 2019 at 15:56. Reason: fixed links
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Old 29th Nov 2019, 20:33
  #824 (permalink)  
 
Join Date: Mar 2019
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Thanks for the information guys - I hadn't known using the manual throttle in the B3 was an issue; seemed simple enough among the pilots I know here in Europe, but the learnings from those reports make for good reading and show even the red CWP procedures which appear simple on paper can be dangerous in the stress of a real emergency.

Anyway, as I said I was simply curious about the accidents relating to confusion between which type was being flown as was mentioned earlier. The main intent of my earlier post was to clarify the question from GOMflyboy76 below, which led to confusion over which variant they referred to:

Originally Posted by GOMflyboy76 View Post
I no longer have the manuals, so can anyone tell me please, AS350B3 Power check when you have "BAD" numbers, what are the parameters? (+/- %)
Per my initial reply, it's safe to assume he's talking about the B3.
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Old 30th Nov 2019, 02:46
  #825 (permalink)  
 
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Originally Posted by JimEli View Post
To my knowledge, I dont believe the + was ever adopted as the official nomenclator, at least never in the US. The RFMs simply refer to the variants as AS 350 B3 Arriel 2B and AS 350 B3 Arriel 2B1. The current model designation is H125, however the RFM is still entitled AS 350 B3e. IMHO, in the US, the manufacturer has always clouded the differences to the point of it ostensibly being a contributing factor in several accidents.

So do you have the answer to the original question by GOMflyboy76 or not?
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Old 30th Nov 2019, 14:26
  #826 (permalink)  
 
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Originally Posted by MitchStick View Post
So do you have the answer to the original question by GOMflyboy76 or not?
Yes.

Dependent upon engine version.

Two charts and a table are utilized to make the determination, there is no +/- %, a check is simply pass/fail. And there are two components to a complete check, TRQ and T4 margin. Furthermore, to my knowledge, under newer versions of the VEMD software, an INCORRECT check is always failure. With older versions of software, you can manually determine an allowance for an INCORRECT T4 MARGIN, but not an INCORRECT TRQ MARGIN. However, in all cases, when computing the EPC manually, one calculates a corrected T4 value. Beyond that, the conditions under which the check were performed are needed to help determine pass/fail.

Oh, and if there is an IBFS installed, it's RFMS probably alters the RFM procedure in some manner.

Last edited by JimEli; 1st Dec 2019 at 20:46. Reason: added info about IBFS
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Old 4th Dec 2019, 13:29
  #827 (permalink)  
 
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Originally Posted by JimEli View Post
Yes.

Dependent upon engine version.

Two charts and a table are utilized to make the determination, there is no +/- %, a check is simply pass/fail. And there are two components to a complete check, TRQ and T4 margin. Furthermore, to my knowledge, under newer versions of the VEMD software, an INCORRECT check is always failure. With older versions of software, you can manually determine an allowance for an INCORRECT T4 MARGIN, but not an INCORRECT TRQ MARGIN. However, in all cases, when computing the EPC manually, one calculates a corrected T4 value. Beyond that, the conditions under which the check were performed are needed to help determine pass/fail.

Oh, and if there is an IBFS installed, it's RFMS probably alters the RFM procedure in some manner.

You kind of answered by not answering.
At least for me being a dumb pilot.

Lets make a practical example

torque tot margin 16.4% on a H125

what do I get from this? The more margin the better?
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Old 5th Dec 2019, 03:49
  #828 (permalink)  
 
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Originally Posted by MitchStick View Post
You kind of answered by not answering.
At least for me being a dumb pilot.

Lets make a practical example

torque tot margin 16.4% on a H125

what do I get from this? The more margin the better?


The OP asked what to do for a failed check. My answer completely covered his options. Basic familiarity with the type would lead to an understanding of what I stated.
As for your contrived and incomplete example, you have a 16.4% margin. More margin is more margin. If you have ever looked at the charts in chapter 5 of the RFM you would fully understand what the margin represents. I would suggest duplicating a VEMD EPC using the charts. No explanation required.

Last edited by JimEli; 5th Dec 2019 at 17:36.
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Old 6th Dec 2019, 10:43
  #829 (permalink)  
 
Join Date: Jul 2017
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JimEli,

Thank you for your input in this thread--getting me back in the books. I have digital versions of the B3e and 2B1 RFMs, but I can't find any differences for the EPs regarding yellow or red GOV lights. Are you seeing anything different? My source materials might be out of date.

Cheers.
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Old 6th Dec 2019, 13:40
  #830 (permalink)  
 
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Originally Posted by tandemonium View Post
JimEli,
Thank you for your input in this thread--getting me back in the books. I have digital versions of the B3e and 2B1 RFMs, but I can't find any differences for the EPs regarding yellow or red GOV lights. Are you seeing anything different? My source materials might be out of date.
Cheers.
You are correct. In the latest versions of the "harmonized" manuals, the procedures are the same.
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