AS350 Astar/Squirrel
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.
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.
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.
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.
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 14:27. Reason: added add'l report
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.
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 14:56. Reason: fixed links
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:
Per my initial reply, it's safe to assume he's talking about the B3.
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:
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.
So do you have the answer to the original question by GOMflyboy76 or not?
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 19:46. Reason: added info about IBFS
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.
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?
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 16:36.
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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.
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.
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.
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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Can someone either explain to me (or point me to a reference doc) how the cycles remaining on the Power turbine are calculated, I believe there are 2 different methods/options?
Thanks
Andy
Thanks
Andy
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Which engine are you operating (or going to operate) - Arriel or Lycoming?
The cycle counting methods vary a bit between each manufacturer. Also for Lycoming / Honeywell there can be different methods of cycle counting depending on which PT disc is installed in the engine.
The cycle counting methods vary a bit between each manufacturer. Also for Lycoming / Honeywell there can be different methods of cycle counting depending on which PT disc is installed in the engine.
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Service Bulletin LT 101-71-00-0002 contains all the information for LTS101-700D2 engine cycle counting and should be accessible via Honeywell's website.
There are two methods for working out the Ng cycles - Method 1 is simpler but it can only be used up to max 103.3 Ng and is also conservative so you may well not get all the cycles out of the engine. Method 2 is a bit more complicated as you have to count 'minor' and 'major' cycles (unless you have Gas Generator Disc 4-111-062-XX with Titanium Impeller 4-11-052-64/-65 installed which eliminates need for minor cycle counting).
Method 1:
Method 2:
Np also needs calculated for each flight - this is based on the maximum Main Rotor RPM and there's a table in the SB.
It's easy to see why electronic cycle counters are popular! Saying that, if you can eliminate the minor cycles from Method 2 then noting the max Ng and max MR RPM for each engine start isn't too arduous.
There are two methods for working out the Ng cycles - Method 1 is simpler but it can only be used up to max 103.3 Ng and is also conservative so you may well not get all the cycles out of the engine. Method 2 is a bit more complicated as you have to count 'minor' and 'major' cycles (unless you have Gas Generator Disc 4-111-062-XX with Titanium Impeller 4-11-052-64/-65 installed which eliminates need for minor cycle counting).
Method 1:
- each engine start = 1.1 operating cycle; each flight during that start ('flight' is defined as a landing / surface contact) = 0.2.
- total Ng operations for each engine start = 1.1 + (landings x 0.2)
Method 2:
- major cycle = max Ng attained between each start and subsequent shutdown (correlate with a table e.g. 96 Ng = 0.5, 97 Ng = 0.6, etc.)
- minor cycle = difference between max and min Ng multiplied by number of operations in this range (correlate with a 'factor matrix' e.g. min 70 Ng to max 102.5 Ng = 0.2)
- total Ng operations for each engine start = major cycles + minor cycles
Np also needs calculated for each flight - this is based on the maximum Main Rotor RPM and there's a table in the SB.
It's easy to see why electronic cycle counters are popular! Saying that, if you can eliminate the minor cycles from Method 2 then noting the max Ng and max MR RPM for each engine start isn't too arduous.
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OK thanks very much for the explanation... I have downloaded a copy of the SB, but I prefer your explanation!
I'm looking to buy a machine and want to establish whether my expected service life will be limited by hours, or cycles.... need to do some maths!
Thanks again!
I'm looking to buy a machine and want to establish whether my expected service life will be limited by hours, or cycles.... need to do some maths!
Thanks again!
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@kiwi_andy No problem at all - glad it was of some help.
If you’ve got a specific aircraft in mind then it’s worth taking a close look at the Power Turbine and Gas Turbine components - different S/N of the same P/N can have varying cycle / hour limits (these should be listed in the SB).
Cycle consumption will certainly be influenced by the type of flying you’ll be doing - lots of heavy load lifting with large fluctuations between max and min Ng can rack up the cycles (unless you can get the disc / impeller combo that does away with minor cycles). Lots of short flights and multiple starts will also quickly eat into your cycles but this is probably true of most turbine engines! The other thing to consider is whether you are frequently going to have to spool down from flight idle to ground idle - this also constitutes a proportion of an Ng cycle and can add up by the end of a busy day.
If you’ve got a specific aircraft in mind then it’s worth taking a close look at the Power Turbine and Gas Turbine components - different S/N of the same P/N can have varying cycle / hour limits (these should be listed in the SB).
Cycle consumption will certainly be influenced by the type of flying you’ll be doing - lots of heavy load lifting with large fluctuations between max and min Ng can rack up the cycles (unless you can get the disc / impeller combo that does away with minor cycles). Lots of short flights and multiple starts will also quickly eat into your cycles but this is probably true of most turbine engines! The other thing to consider is whether you are frequently going to have to spool down from flight idle to ground idle - this also constitutes a proportion of an Ng cycle and can add up by the end of a busy day.
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thanks again for the further clarification, and useful info. I will ascertain what Gas Generator disk is fitted.
Without a cycle counter fitted, there may be scope for the accuracy of any previous operators correctly counting cycles to affect the real cycle count particularly if the operating environment is quite varied.
Without a cycle counter fitted, there may be scope for the accuracy of any previous operators correctly counting cycles to affect the real cycle count particularly if the operating environment is quite varied.