rharshberger
Well-Known Member
Actually yes some of us do, having two people with actual experience chime in and give facts NOT based on the media was well worth it.
Rogue Boeing 737 Max planes ‘with minds of their own’ | 60 Minutes Australia
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And this is why the current "new" controversy over the certification basis for the 737-10 is going to be hard. The biggest reason we (Boeing) argued against changing the alerting system on the first members of the Max family (737-8, -9) was that flight crews were going to be going back and forth between them and 737-700s, -800s, and -900s and that carrying over the older 737 family crew alert system was believed to be safer than introducing something EICAS-like on the Max family and having those same crews get confused at just the wrong moment.
And yes, putting an EICAS-like system into the 737 will be a very hard, very disruptive thing, including for systems that are unchanged on the Max from the Next Gens, so it will also be costly and create the opportunity for what software folks call "regression bugs" if is forced to be done.
In my opinion the -10 (and the -7, which is further along but I don't think yet certified either) should have the same crew alerting system as the other thousands of active 737s, not be different. But my opinion is that of an over five years retired configurator, and is worth exactly what you paid for it!
I have no idea where this will go now that the politicians, as well as the folks at the FAA and at my former employer, are going to have to be in the act.
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Aviate. Navigate. Communicate. The golden rule of flying.
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And thank you Mach 7 for your expert evaluation.
Perhaps you can clear up something that's confusing me. The head of the AA pilots union, a veteran 737 pilot who also flew the Max said the Ethiopian pilot did everything he was trained to do. The MCAS pitched the nose down so aggressively that it was unrecoverable. So what went wrong? Is the recovery procedure on Speed Trim the same as on MCAS? If not were the two flight crews trained on the MCAS procedure? Did they even know it was part of the plane? In your opinion would the crashes be mainly attributable to defective hardware/software design or pilot error, or a combination of the two?
And any new MicroMaxx builds?
I have never met the APA union pilot, nor have I heard/read what you attest him to have said. I do not doubt it,
I just have no knowledge of it.
I can not comment other that to guess he had not read the entirety of the accident report. Perhaps he made that statement before the reports were released? Based on media reports?
Anyway, lets look at the 737 Stabilizer trim system.
The horizontal stabilizer is the small "wing" at the aft of the aircraft, under the vertical stabilizer.
The Elevators are attached to the back of the horizontal stab.
The only way the horizontal stab can move is through the electric trim motor. This is the only way the horizontal stab can move. Sort of, more later.
We use the trim to remove control forces while we fly. The pilots each have switch on our control yoke to activate it.
The autopilot also uses the electric trim system when it is being used.
When the 737-300 had the high bypass CFM engines installed, the much greater diameter of the engine required the engine to be lowered below the wing, this creates a moment arm with the thrust that tends to pitch the nose up when adding power. The FAA decided that if a pilot was not paying attention while adding power the pitch might increase too much so they had Boeing add "Speed Trim" to lower the nose under certain conditions. Speed trim has been on ALL 737's from the -300 on. Speed trim uses the stabilizer trim system to lower the nose. It's a pain in the ass. I'm flying the plane, I know what trim/control forces I need to make the aircraft do what I want. Speed trim always moves the trim opposite what I want. The operational "fix" is to click the trim every so often because speed trim is deactivated for 5 seconds after the pilot adds trim.
When the MAX was being certified it became apparent that the LEAP engine/nacelle caused a greater than expected pitch up under certain conditions.
And here is Boeing's mistake, rather than redesign speed trim, they added MCAS to it. This was a quick fix to keep the certification on track, pilot training was never a consideration. This was/is not a fatal flaw, apparently they did not listen to some of the engineer's on the fix who wanted a more involved fix, nor did they inform the FAA.
Boeings logic was the pilots have a runaway trim memory procedure, Speed trim and MCAS use the trim system so if they failed it would manifest as a runaway trim and the pilots would do the correct procedure. This is entirely logical and not unreasonable. And the reason I don't care if MCAS was in our manuals or not. What I care about is that I can correct a fault. Which I can with MCAS, and could with MCAS as installed on both accident aircraft.
Now MCAS uses the stabilizer trim system to move the pitch of the aircraft down. If the stabilizer trim cutout switches are switched to cutoff, as the runaway stabilizer memory item requires, ALL electrical power is removed from the trim motor. MCAS can not move the nose down anymore. Period, end of story.
As MCAS uses the trim motor, it can not move faster than the regular trim system. So it is not a super agressive trim. Further the 737 is certified and demonstrated to be flyable with the trim stuck in the full nose up or down position. The Elevators can easily over come full trim, it's not fun but it is flyable.
If you guys want to get into the manual trim option, I'm happy to address it, but it has limitations that were not addressed by either accident crew.
I hope this helps everyone understand what happened and why.
And sadly, no I have not been able to build any more micro's. Though I do have a few in the que!
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Thank you for the clarification.
Yes, the statement by Dennis Tajer was just after the second crash.
"Tajer, who has flown the 737 MAX, argues the Ethiopian Airlines pilots did what they were instructed to do but that Boeing’s MCAS forced the plane into such an aggressive downward angle that the pilots could not recover.
“They had wired that thing so that it was irrecoverable. It just blew us away,” Tajer said."
https://www.cnn.com/2019/05/23/business/american-airlines-boeing-pilots-union/index.html
I have read the final report by Indonesian investigators on the Lion Air crash. They do not cite a primary cause of the crash, but list a number of issues that contributed to it.
The Ethiopian Air crash investigation has released a preliminary and an interim report but as far as I can find not a final report yet. It was said that it would be released "soon" on March 2021. That was over a year ago. There may be a difference of opinion between parties, I'm guessing.
Anyway, for anyone interested here are the two crash investigation reports (Lion Air final and Ethiopian Air interim). Each person can decide for themselves which factors were critical. I'm staying out of it.
https://www.flightradar24.com/blog/wp-content/uploads/2019/10/JT610-PK-LQP-Final-Report.pdfhttps://context-cdn.washingtonpost....note/8ba51389-8298-4c08-8ef6-6416b262fd1b.pdf
Peace.
Aviation accident reports take a long time. The Ethiopian report out is the interim report, I expect COVID has delayed the final report. Reports outside of the US can also be somewhat political in nature. Trust the data. Bravo52 posted the FDR data graph, it can be difficult to read, but its all there.
In any event, we do know what happened, the CVR and FDR have been thoroughly evaluated.
Capt Tajer is wrong. I have flown the scenario and recovered, as have all 2000 737 pilots at my airline. Some of our pilots have flown the old MCAS scenario and had no problem recovering. A few called it a "handful", but had no problem. We get paid to bring back our passengers even when the aircraft fights us.
Peace indeed,
Maybe on my next HNL layover I can bring a few micro's and we can launch!
In any event, we do know what happened, the CVR and FDR have been thoroughly evaluated.
Capt Tajer is wrong. I have flown the scenario and recovered, as have all 2000 737 pilots at my airline. Some of our pilots have flown the old MCAS scenario and had no problem recovering. A few called it a "handful", but had no problem. We get paid to bring back our passengers even when the aircraft fights us.
Peace indeed,
Maybe on my next HNL layover I can bring a few micro's and we can launch!
Good points Pat!
Good to see your post.
Yah, Southwest's roll in the some MAX decisions are interesting.
rharshberger
Well-Known Member
My read on Mach7's statement is that the "old" and "new" MCAS scenarios were done on simulators, not actual flights. Don't see how the "old" scenario could be run on an actual flight if all Maxs have been upgraded. Mach, correct me if I'm wrong.
The whole back and forth on the other thread (before it was moved here) was about this statement:
From reading the Lion Air final report it is apparent that the crew initiated procedures they were taught to deal with the problem. What they did not know about was the MCAS augment and dealing with repeated activations. From the report (red highlights mine):
27. Boeing considered that MCAS function is automatic, the procedure required to respond to any MCAS function was no different than the existing procedures and that crews were not expected to encounter MCAS in normal operation therefor Boeing did not consider the failure scenario seen on the accident flight. The investigation believes that the effect of erroneous MCAS function was startling to the flight crews.
28. The investigation believes that flight crew should have been made aware of MCAS which would have provided them with awareness of the system and increase their chances of being able to mitigate the consequences of multiple activations in the accident scenario.
29. Without understanding of MCAS and reactivation after release the electric trim, the flight crew was running out of time to find a solution before the repetitive MCAS activations without fully retrimming the aircraft placed the aircraft into in an extreme nose-down attitude that the flight crew was unable to recover from.
30. Flight crew training would have supported the recognition of abnormal situations and appropriate flight crew action. Boeing did not provide information and additional training requirements for the 737-8 (MAX) since the condition was considered similar to previous 737 models
I agree, it is one thing to successfully pass a scenario with knowledge of a subsystem and what it can do and having the training and procedures to successfully deal with it. The Lion Air and Ethiopian Air flight crews did not have that luxury.
Anyhoo I don't think there is a single Max crew worldwide that doesn't know about MCAS and proper procedures to deal with it by now. Changes have been made to MCAS and its' software. It can no longer be activated by a single (faulty) sensor. Two AoA sensor readings are compared and if there is a discrepancy the subsystem does not activate. The maximum stab deflection has been reduced. An AoA discrepancy warning light which was only available as an $80,000 option is now standard (IIRC). And I believe I read somewhere that pulling back the command column will activate a cutoff of MCAS. Again, correct me if I'm wrong. I am admittedly a layman, but a voracious reader.
I stated in my 2+ yr. old post that the 737 Max was one of four craft that I would not risk travelling on. That was true then but today it is probably the most scrutinized aircraft ever, and I would have no qualms about boarding one now.
Laters.
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kuriirin, We have never met, But I enjoy the majority of your contribution on the forum. I feel we would get along very well in person.
Sometimes semantics are lost while typing, and your statements are always compelling.
So take what I'm going to say with that in mind.
27:
Startling to the flight crew.
WHAT THE F@CK!
ANYTHING THAT IS OUT OF THE NORM IS STARTLING.
Was I Startled when ATC made an error and I had a G3 pass 100 ft off my left in solid IFR?
Was I startled when the fire seal gave out on the left engine of my T-37 instantly filling the cockpit with very hot smoke?
Was I startled when my nose gear indication went red in the flare?
Was I startled when we hit a large bird at 100 ft and it almost completely blocked the windscreen, while in the clouds?
Was I startled when we hit extreme turbulence at 1000ft on approach and I could no longer read the instruments because we were bouncing so violently?
Was I startled when the hot bleed air duct ruptured on the number 2 engine instantly filling the cabin
with 180F high pressure air?
Was it startling when at cruise at FL330 every caution/warning system suddenly started to scream at us?
Was it startling when a passenger went into seizures while 70 miles from a recovery base and I had to fly at 340kts until 15 miles from landing to get her to medical attention?
Was it startling when I got an indication that a SA-2 was tracking us?
Anything that can kill in an airplane is startling!
The 1st rule to staying alive in aviation is to fly the aircraft!
In the simulator and on the line when anything odd happens I always do a quick scan and make an immediate
assessment, its either "We are flying" or "We are not flying". Thankfully its almost always been the 1st.
with both accident crews it was "We are flying"
After you make sure you are flying you need to rapidly asses what will stop you from flying and deal with that.
Usually what will stop you from flying will be the ground, the ground always wins.
28. Great, the investigation believes....
That and $4 will get you a cup of coffee at Starbucks.
Hypothetical opinion.
Here is a fact. If the crew had done the runaway stab trim memory procedure they would have recovered the aircraft.
30. Here is the important part:
"condition was considered similar to previous 737 models"
The recovery procedure for the issue was the same as all previous 737's.
The bottom line in both accidents is both crews did not accomplish the procedure that would have recovered
the aircraft. The procedure, at the time was:
Control column- grasp firmly
Autopilot/auto throttles- disconnect
If runaway continues- Stab trim cutoff switches, both, off
Thats it, done end of story. Those 3 simple steps would have recovered both aircraft.
And yes, moving the control column opposite (nose up here) the runaway trim will cut of the electrical
trim. As will activating either trim switch, for 5 seconds.
As I have stated, I have had an instructor give me full nose down runaway trim at liftoff, this is a faster trim
speed than the original MCAS system, and he failed the control column cutout switch at the same time.
This was years before the MAX, in 2001. was I startled? YES!. Did I fly the aircraft? YES. Did I do the above procedure? YES! I got clear of the ground, cleaned up the aircraft declared an emergency and came back and landed.
This was in the simulator, we NEVER train emergency procedures in the aircraft. The simulator training is VERY
good and VERY realistic. So much so that the FAA allows me to log sim time as actual flight time. I don't, but I could.
Sometimes semantics are lost while typing, and your statements are always compelling.
So take what I'm going to say with that in mind.
27:
Startling to the flight crew.
WHAT THE F@CK!
ANYTHING THAT IS OUT OF THE NORM IS STARTLING.
Was I Startled when ATC made an error and I had a G3 pass 100 ft off my left in solid IFR?
Was I startled when the fire seal gave out on the left engine of my T-37 instantly filling the cockpit with very hot smoke?
Was I startled when my nose gear indication went red in the flare?
Was I startled when we hit a large bird at 100 ft and it almost completely blocked the windscreen, while in the clouds?
Was I startled when we hit extreme turbulence at 1000ft on approach and I could no longer read the instruments because we were bouncing so violently?
Was I startled when the hot bleed air duct ruptured on the number 2 engine instantly filling the cabin
with 180F high pressure air?
Was it startling when at cruise at FL330 every caution/warning system suddenly started to scream at us?
Was it startling when a passenger went into seizures while 70 miles from a recovery base and I had to fly at 340kts until 15 miles from landing to get her to medical attention?
Was it startling when I got an indication that a SA-2 was tracking us?
Anything that can kill in an airplane is startling!
The 1st rule to staying alive in aviation is to fly the aircraft!
In the simulator and on the line when anything odd happens I always do a quick scan and make an immediate
assessment, its either "We are flying" or "We are not flying". Thankfully its almost always been the 1st.
with both accident crews it was "We are flying"
After you make sure you are flying you need to rapidly asses what will stop you from flying and deal with that.
Usually what will stop you from flying will be the ground, the ground always wins.
28. Great, the investigation believes....
That and $4 will get you a cup of coffee at Starbucks.
Hypothetical opinion.
Here is a fact. If the crew had done the runaway stab trim memory procedure they would have recovered the aircraft.
30. Here is the important part:
"condition was considered similar to previous 737 models"
The recovery procedure for the issue was the same as all previous 737's.
The bottom line in both accidents is both crews did not accomplish the procedure that would have recovered
the aircraft. The procedure, at the time was:
Control column- grasp firmly
Autopilot/auto throttles- disconnect
If runaway continues- Stab trim cutoff switches, both, off
Thats it, done end of story. Those 3 simple steps would have recovered both aircraft.
And yes, moving the control column opposite (nose up here) the runaway trim will cut of the electrical
trim. As will activating either trim switch, for 5 seconds.
As I have stated, I have had an instructor give me full nose down runaway trim at liftoff, this is a faster trim
speed than the original MCAS system, and he failed the control column cutout switch at the same time.
This was years before the MAX, in 2001. was I startled? YES!. Did I fly the aircraft? YES. Did I do the above procedure? YES! I got clear of the ground, cleaned up the aircraft declared an emergency and came back and landed.
This was in the simulator, we NEVER train emergency procedures in the aircraft. The simulator training is VERY
good and VERY realistic. So much so that the FAA allows me to log sim time as actual flight time. I don't, but I could.
Mark, I think we are mostly in agreement. As you say, semantics and interpretation are the stumbling blocks.
A previous Lion Air flight had encountered multiple MCAS activations. The flight crew activated the stab trim cutoff switches and the captain manually landed the plane.
The FO on the fatal flight was attempting to complete the NND but did not apply sufficient electrical trim to counter multiple MCAS activations.
Command column cutoff of MCAS is a modification implemented after the two crashes.
Too bad it was not available to the pilots of the fatal crashes.
It appears they were fighting like hell to control the situation.
In any event, if I do decide to board a Max in the future, I hope you're the captain (or someone like you).
Laters.
A previous Lion Air flight had encountered multiple MCAS activations. The flight crew activated the stab trim cutoff switches and the captain manually landed the plane.
The FO on the fatal flight was attempting to complete the NND but did not apply sufficient electrical trim to counter multiple MCAS activations.
Command column cutoff of MCAS is a modification implemented after the two crashes.
Too bad it was not available to the pilots of the fatal crashes.
It appears they were fighting like hell to control the situation.
In any event, if I do decide to board a Max in the future, I hope you're the captain (or someone like you).
Laters.
There is some initial indication from Boeing that pulling the yoke aft to counter MCAS would not cut out the MCAS movement in the pre grounding aircraft. This is counter to what we are taught. The yoke switch is a physical electrical ground cut out. It is in place to help counter runaway trim and SHOULD have nothing to do with MCAS itself.
Let me do some research on that. It is possible Boeing bypassed the switch on the 1st gen MCAS aircraft, though I can't think why. It's also possible that the statement by Boeing was made in error. I'll look into it.
EDIT:
Thank you kuririn for the kind words. They are appreciated.
Let me do some research on that. It is possible Boeing bypassed the switch on the 1st gen MCAS aircraft, though I can't think why. It's also possible that the statement by Boeing was made in error. I'll look into it.
EDIT:
Thank you kuririn for the kind words. They are appreciated.
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I'll have to revise that to say MCAS has been modified so that it can never apply more force than the command column can counter.
From the Lion Air investigation final report:
1. Updates to the MCAS
• The flight control system will now compare inputs from both AOA sensors. If the sensors disagree by 5.5 degrees or more, MCAS will not activate. An indicator on the flight deck display will alert the pilots.
• If MCAS is activated in non-normal conditions, it will only provide one input for each elevated AOA event. There are no known or envisioned failure conditions where MCAS will provide repetitive inputs.
• MCAS can never command more stabilizer input than can be counteracted by the flight crew pulling back on the column. The pilots will continue to always have the ability to override MCAS and manually control the aircraft.
IIRC the cascading activations resulted in a force of 100# on the stick where 75# is the max standard. Also if I read the above correctly the multiple activations of MCAS has been changed to only one.
... Many airframes had only 1 AOA sensor. No way to detect bad data ...
All Maxes have one on each side of the nose. And with the fix to MCAS both will be active with respect to that system on every flight rather than switching from one to the other each time the airplane is powered on as was done initially.
They did not, originally; duals were a $$ option.
Like we've been saying, all the pilots are blaming the other pilots, when the entire situation was a CF of greed, neglected oversight, poor industrial design and unobvious undiscoverable affordances, software engineering failures, the list goes on.
I do not understand why living pilots are so compelled to blame their colleagues, when this was a system failure from top to bottom. I'm not a psychologist so I won't make any guesses about pilot delusions and motivated reasoning. But I will point out the abundance of literature on the topic, about aircraft, and other industrial systems.
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You're making me try to remember all the NG options that we carried over to the Max and what was made standard. One of my tasks in the Configuration group was to work on that thing. I just don't remember about this one now. I thought (and maybe mis-remembered) that dual AOAs were standard, even on the NG.
What airline didn't take that option? Do you know of one by name?
Both fatal crashes of the Max, Ethiopian Air, and Lion Air
https://www.cnn.com/2019/04/30/politics/boeing-sensor-737-max-faa/index.html
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All 737s have two AOA sensors on the aircraft. This included/includes the MAX. The AOA Indicator system was an option that was not purchased by some airlines. Basically, that system would indicate when the data streams were providing different data as in the case of a sensor failure. Before revision, MCAS only took data from a single AOA data stream so if the offending sensor providing data failed, the MCAS failed to function properly if continued to be used.
Actually, everything cls has said has been pretty spot on.
*Edit* Wait, wait, I didn't read a the way through. Reserving judgement.
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Bravo52 is correct. All 737's have 2 AOA sensors. Always have.
kuririn,
I was wrong on the trim cutout yoke switch. It is not a simple ground interruption as I thought. There are 2 logic switches on the yoke. One for forward movement and one for aft movement. They are independent of each other. So it could have been wired so MCAS would bypass it.
Yes MCAS now looks at both AOA vanes before activation, before it only looked at one. There is also, now, a third virtual AOA vane. Generated by the Inertial reference units. This gives the aircraft triple redundancy now.
And yes MCAS now can only have one activation per flight.
I want to stress a point here again. MCAS can only act through the existing stabilizer trim system. It does not have it's own actuators. Any forces it puts on the control yoke, through the stab trim, can not exceed a "normal" stab trim runaway. The aircraft (Classic/NG/MAX) is, and always has been, certified to have sufficient control response with FULL stab trim deflection. Nose up or nose down.
kuririn,
I was wrong on the trim cutout yoke switch. It is not a simple ground interruption as I thought. There are 2 logic switches on the yoke. One for forward movement and one for aft movement. They are independent of each other. So it could have been wired so MCAS would bypass it.
Yes MCAS now looks at both AOA vanes before activation, before it only looked at one. There is also, now, a third virtual AOA vane. Generated by the Inertial reference units. This gives the aircraft triple redundancy now.
And yes MCAS now can only have one activation per flight.
I want to stress a point here again. MCAS can only act through the existing stabilizer trim system. It does not have it's own actuators. Any forces it puts on the control yoke, through the stab trim, can not exceed a "normal" stab trim runaway. The aircraft (Classic/NG/MAX) is, and always has been, certified to have sufficient control response with FULL stab trim deflection. Nose up or nose down.
KC3KNM
Probably Wrong
Do you have any insight as to why they'd only reference a single AOA sensor before the crashes/updates? It seems insane to have redundancy built in but ignore the second sensor in MCAS.
It's not all that uncommon in older narrow body aircraft to have single point failures on non critical systems.
I know the MAX is a "new" aircraft but it is certified under the original 737-100 certificate with modifications.
My type rating from the FAA says B-737, that covers all 737's from the -100 to the MAX. I would NOT feel qualified to fly a 737-100 or -200, but to the FAA they are all the same. Thats a decision that the FAA should be rethinking.
I also want to make one thing clear, I'm not absolving Boeing of making a bad decision with MCAS.
In its original design it was a quick, sloppy fix. My opinion is that they went with that design to keep the certification on time and had nothing to do with money, but that is my opinion.
It's a decision that Boeing regrets to this day, and they may have bet the company on it.
What I am saying is that the 2 accident crews had a procedure that would have recovered the aircraft, and they did not correctly accomplish it.
I know the MAX is a "new" aircraft but it is certified under the original 737-100 certificate with modifications.
My type rating from the FAA says B-737, that covers all 737's from the -100 to the MAX. I would NOT feel qualified to fly a 737-100 or -200, but to the FAA they are all the same. Thats a decision that the FAA should be rethinking.
I also want to make one thing clear, I'm not absolving Boeing of making a bad decision with MCAS.
In its original design it was a quick, sloppy fix. My opinion is that they went with that design to keep the certification on time and had nothing to do with money, but that is my opinion.
It's a decision that Boeing regrets to this day, and they may have bet the company on it.
What I am saying is that the 2 accident crews had a procedure that would have recovered the aircraft, and they did not correctly accomplish it.
As others have noted, and as I had thought, dual angle of attach sensors are standard on all 737 NGs and Maxs. Considering the installation and how having an option for only one would ripple all the way back to the fuselage build in Wichita, or, if the provisions were standard but the sensor itself (and wiring, I suppose) were optional such an option would require the installation of a cover over a fairly large hole in the fuselage skin on one side of the nose, a cover good enough to hold against airplane pressurization in place of the not-taken AOA vane. It really doesn't even make sense that a single AOA vane would be optional.
The CNN article you cited does NOT disagree. It says that the initial implementation of MCAS relied on data from one of these at a time to perform its function. That was also correct at the time. As I noted before, which of the two AOA vanes the original implementation of the system would take its data from switched sides every time the airplane was powered up.
The option you are referring to was for an added cockpit indication that the AOA sensors disagreed. It was then optional and now standard on Maxes.
NateB
Well-Known Member
I was surprised when I learned how many changes can be made and still be a model variant. We have an older generation ship in the fleet as a backup (As365n as opposed to the N2 models as our front line aircraft) which has smaller fenestron blades, less HP, smaller tail fin and different stabilization features. As such, not all of our pilots are company qualified to fly it, even though for FAA purposes it is the same.
