Just a Theory:)

Spoke to a pilot who was in one of the first 407 tailrotor seperation accidents.He managed to land the beast in one peace.

This is his explenation:
"I was flying along by myself doing about 126kts indicated when all of a sudden the tail yawed to the left. I entered a auto and landed safely.My explenation is that the leading edge on the t/r blade delaminated causing enough friction to brake the shaft.The blades then flaped excessively and cut off the tail with the remaining momentum."

:}
He's theory did sound convincing.
Could this be true:confused: :uhoh: :ugh:

I'm thinking that such a failure should also have caused a torque spike, which should have been recorded in the FADEC memory? After all, there would have to be a lot of power added to break the shaft, the governing system would have added power to maintain RRPM as that blade failed?

just throwing out thoughts.

Bell 407
 

I've been told PHI has grounded its 407 fleet.

My source told me a fault with the No.3 turbine is suspected following recent crashes and that, with Rolls Royce support, PHI is replacing it throughout its entire fleet of about 35 aircraft.

Fact? Or false rumour?

Unfortunate timing perhaps ... a new press release has come in..

The Bell 407 fleet has surpassed the 1,000,000 flight hours mark. The major milestone was reached in November. One million hours, that equals a little more than 114 years or just less than 11 and ½ decades or around 41,667 days. No matter what terms you use to describe it, 1 million hours is a lot of time.

A lot of it about ... MD just annouced 500,000 NOTAR fleet hours...

500,000 NOTAR fleet hours
 

.......With a struggle......:\ ....its a labour of love:)

From what I hear, there is a bulletin out on the turbine blades, some were defective and recalled, but more were found defective when they were inspected. Rolls-Royce may have a big problem here. The PHI fleet has been grounded indefinitely, it seems, and are being covered by 206s for the time being. It might behoove other operators to do the same thing. People are dying in 407s, and not inspecting them could be found to be negligence if lawsuits were to be filed, leading to very large jury awards. Rolls-Royce could have lots of liability here. Just speculation, you understand.

which engine have they in the 407 steve

As Gomer says the PHI 407 fleet remains grounded due to suspected engine issues with the C47. According to sources, PHI will not "unground" the fleet until suspect engines have been replaced.

PHI 407s with new engines are to be back flying this week.

STRANGE - From the ASB CEB–A–72–6048 issued on 2nd OCTOBER (and revised on 6th) and further covered by Bell ASB 407-03-61 (issued 21nd NOVEMBER):

"Recently, an incident was experienced in which a 4th–stage turbine wheel (23066744) was found to have an over blended, thin trailing edge. Although blending is a common procedure for turbine wheels, in this particular case the turbine wheel blade trailing edge was blended beyond print requirements. All Rolls-Royce Model 250–C30, –C40 and –C47 series 4th–stage turbine wheels (23066744), S/N X504345 and earlier require a one-time inspection to verify that the blades do not have a thin trailing edge."

"For 4th–stage turbine wheels (23066744, S/N HX76702 to HX76755): Compliance Code 2. Turbine wheels which have over 1000 hours must be inspected within the next 150 hours. Turbine wheels which have less than 1000 hours must be inspected within the next 300 hours or at 1000 hours, whichever comes first."

Inspection is with a simple go-no gauge and can be done installed. Failure requires removal of wheel and fitment of new blades.

NOW.... OPTIONS
a) this ASB could be just a coincidence and there is a further problem with 3rd stage (though no ASB or FAA EAD issued as yet to my knowledge)
or
b) 10 weeks after the ASB is issued, an operator with many affected 407s with >1000 hours on their turbine wheels have used up the 150 hours and not having yet done the checks are thus grounded
or
c) 10 weeks on the inspection failure rate is outstripping the overhaul shops' ability to replace the blades
or
d) things have moved on, the problem is (or is seen as) more serious and PHI have judged the inspection is not sufficient

Zalt

Problem suspected as per Flying Lawyer with No.3 wheel, not No.4 wheel.

Your (d) is correct and PHI will replace suspect engines as well as replace all wheels on a continuous basis at less than 1000 hours total time.

Hip:cool:

for engineers out there is this the same 47 that i have in my 600 steve

Steve,

If you - or any of our other Model 250-C47B/47M operators - have any concerns regarding the current engine investigation, as described in the Bell Service Letter posted below (Bell ASB 407-03-73), I would strongly encourage you to contact the customer support team here in Indy ([email protected] or phone: 317 230 2720).

Since the investigation is still on-going, it's not appropriate for me to provide further comment on the root cause (as much as I might want to), but I will say that the current focus of the investigation is on the -C47B/407 rather than the -C47M/MD600N, due to differences in the engine running speed.

There is a substantial effort being undertaken by the team here in Indy (in cooperation with Bell and the NTSB) to fully understand and address this issue, and further information will be released through the proper channels as soon as it is known.

Fly safe,
t/shaft

-----

Information Letter 407-03-73
December 14, 2003

TO: All Owners/Operators of Bell 407 series Helicopters
SUBJECT: Information on Model 407

There have been 2 incidents in the Texas gulf coast area involving the Model 407 since November of this year. The preliminary investigation suggests that they may be engine related. The investigation by the NTSB is on going at this time.

Both Bell and Rolls-Royce have formed a joint action team to ensure that the combined assets of both companies are focused on the most rapid resolution of the situation. The engine components have been returned to Rolls Royce under the authority of the NTSB investigation. Important information resulting from the investigation will be distributed rapidly to all the Model 407 operators and maintainers as it becomes available.

Currently there are over 560 Model 407 Rolls-Royce powered helicopters in over 80 different countries around the world. This fleet has accumulated over 1,400,000 flight hours since the introduction in 1996.

Bell Helicopter and Rolls-Royce are committed to the rapid resolution of these events and our desire to keep you well informed.

Any media inquiries regarding these incidents may be directed to Carl Harris in the Bell Helicopter Textron office (phone: 817-280-2783, email: [email protected] ).

Customer inquires may be directed to Jack Denham, Director Product Support (phone: 817 280-3344, email: [email protected] ).

In case of questions about the involvement of the engine:

Please direct any media inquiries regarding this incident to Maria Weber in the Corporate Communications office (phone: 317-230-6662, email: [email protected] ).

Please direct any customer inquiries regarding this incident to Gary Souza in the Model 250 support team (phone: 317-230-3987, email: [email protected] ).

600 Driver,
To the best of my knowledge, the actual engine is the same, the only difference is the software.

A very interesting item in the BHT IL is that there have been '2 incidents in the Texas gulf coast area involving the Model 407 since November of this year'.

There are no relavent entries in the NTSB accident database.

This either suggests these were truely more minor incidents (and not related to 'people dying in 407s' as speculated above) or as discussed in past posts, that the US system is supressing events that other countries would class as accidents.

It would be REALLY useful if anyone of those people close enough to have confirmed the PHI groundings / wheel changes could actually say what happen in these 2 incidents.

Meanwhile, a trivial point - how come the fleet hours have gone from passing 1 million in November to 1.4 million now?

EDIT: After looking through past threads, the ditching of N405PH just after take off from a rig nine miles south of Marsh Island (reported on 16 Nov) is probably one. The absence of this accident from the NTSB database is rather worrying.

Zalt

N405PH was a ditching after take off.

It is not in the NTSB accident database because it was not classified as an "accident" but as an "incident".

No significant damage occurred to the aircraft as a result of the ditching and significant damage (in the opinion of the NTSB investigator assigned) is one of the criteria used to determine whether it is an accident or incident.

LE

Accidents aren't listed in the NTSB database until a preliminary report is issued. Apparently the NTSB is still investigating the 407 accidents. There have been at least 2 fatal 407 accidents, neither of which is on the NTSB site, but which have been reported on the FAA preliminary accident site. The FAA reports accidents as they are reported to it, and the information is often sketchy, and sometimes incorrect. The NTSB only issues a report after a probable cause is determined, or when it's a major airline accident, it may release information while the investigation is still ongoing. It's not unusual for accidents not to be listed on the NTSB site for some weeks if a probable cause is not obvious. From the FAA descriptions, the causes of the 407 crashes probably weren't completely self-evident.

B 407 Fennestron??
 

Hi All,

I found this while doing a bit of surfing, sounds interesting!!

(quote)

"Although Bell won't unveil an all-new helicopter model, Redenbaugh says he will announce a plan for developing new and improved models at the Helicopter Association International Heli-Expo trade show Sunday.

He declined to discuss specifics, but sources within Bell say engineers are working on three projects that could lead to improved aircraft within a couple of years.


A tail-rotor shroud, known as a fenestron, is being designed and will be tested on a Bell 407, the company's bestselling helicopter. Used for years by other manufacturers, the shroud produces a quieter aircraft and reduces the risk of someone being maimed by the tail rotor"

A fenestron type tail rotor is not new to Bell, they dabbled about ten years ago with a 'ring tail' on the 400 [a pre-427 twin]. It was minimalist and probably did little more than mark and guard the outer tail rotor. They dropped it and the 400.

Bell did produce some pictures of a new project using a 'proper' fenestron at HAI - potentially a 206 replacement. It was described as a Gazelle lookalike and that was a fair description.

Bell's model 400......

http://avia.russian.ee/vertigo/foto/bell_400.jpg

As one of the few to have actually flown the Bell 400, I could never figure out why they didn't do anything with the ring-fin concept.
Seemed to have lots of benefits and few drawbacks.

The new tail design is a prototype being developed on using a 407 body as an experimental look for the proposed new model line, MAPL. (Modular Affordable Product Line) This will be a new family of helicopters designed around a new rotor system, tail rotor, drive system, cabin, and engine. Proposed concept includes light single, light twin, and medium twin models, all based on same family of parts.
Bell will also be evaluating a new rotor system (possbily also using a 407 body) as part of the research for this new development program. This work is being conducted at Bell's XWORX R&D facility.

From HAI press release:
Bell’s Modular Affordable Product Line (MAPL) of helicopters is making significant progress as development continues on the technologically advanced products. Plan calls for aircraft to be designed, built and certified by the end of the decade.

Bell began development last year of the technology for MAPL, a family of light helicopters, including both single and twin-engine models. The MAPL family is being designed to provide break through productivity gains for Bell customers.

Bell market research on the MAPL concept has shown us that our customers’ price is the clear driver of customer satisfaction and that our initial targets of speed, payload, and noise are preferred. In response to our customers some of the design characteristics designed into the aircraft are:

20% productivity improvement via speed and useful load improvements
20% reduction in operating costs
10 dB noise reduction
99% dispatch reliability
In order to achieve the high reliability rating desired, Bell has embarked on technology maturation for the MAPL family. Key technologies being developed by Bell include the main rotor, drive train, autopilot, and noise control. In addition, suppliers are working on engine technologies and avionics to meet customer requirements

To provide customer desired comfort along with affordability, Bell designers have developed fuselage concepts providing more space for pilots and passengers. By developing a modular construction technique offering significant commonality across the product line, Bell’s investment and recurring costs are reduced thus providing a more affordable product for our customer

In keeping with Bell’s aim to provide current customers with product improvements, engineers are also working on a plan to insert MAPL technology into our existing product line. This will benefit the customer in two ways: first by improving the performance and cost of Bell’s legacy products and second by maturing key technologies in service before the MAPL aircraft enter service.

Bell have a picture and article here.

http://www.bellhelicopter.textron.co...51_profile.jpg

Bell misleads 407 owners
 

After the numerous crashes involving Bell 407's, mainly due to the tail rotor hitting the boom or the boom breaking off, Bell introduced all sorts of quick fix solutions, and promised their 407 owners that they have come up with the solution, and that all is well.

Not so, Bell! A Bell 407, ZS-RLS, belonging to a Cape Town based helicopter operator, was involved in such an incident recently.

The pilot landed, ran down the engine for 2 minutes, then shut it down. After the engine was shut down, he heard a scraping noise, and an investigation to the tail after the blades had stopped, revealed that the tail rotor had hit the boom. Now where is the fix now dear Bell people?? Thank God it did'nt happen in flight, because then that helicopter and its occupants would have become another statistic.

This is the first time ever that Bell is now in a position to evaluate the situation, as everything on the helicopter is intact. During the 407 crashes, the helicopters were normally totally destyroyed, so Bell could not say what caused it. Here is the evidence. The "quick fix" that Bell promised, has failed, and all 407's should therefore regarded as suspect.

It is alledged that the South African Bell rep inspected the helicopter, and he could offer no solution, as the pedal stops were'nt open. A SACAA inspector had a subsequent discussion with the Bell rep, and wanted to know if Bell intended grounding the fleet, to which the Bell rep responded 'negative".

Now I would say that that is a very irresponsible approach, as for the first time now there is a 407 in one piece, on the ground for Bell to evaluate the problem, and Bell says "no thanks"

It is believed that all the 407 crashes was the result of the tail rotor hitting the boom, the boom then breaking off due to excessive vibration, and the helicopters being totally destroyed in the process.

I will not risk my life poling a 407, and all 407 operators should take note of this incident, and pressurize Bell into doing something about it.

This is not to support Bell, or to say that they shouldn't fix things, but isn't it true that nobody has been killed yet through this? That's what I was told when I did my conversion. It appears to be quite good without a tail rotor, relatively speaking. It's a fine ship, and you could argue that the AStar should also be grounded after the recent series of control hardovers which definitely have killed people, and make me wary of flying it until they have sorted it properly (not to mention other slightly cheesy things).

You are assuming, of course, that all the mods were done correctly, or even done at all.

Let's not get too hysterical.

Phil

I have read this posting with interest.

As far as I know, out of all the 407 accidents where the boom broke off, only on two occassions did the occupant(s) survive.

I saw the remains of a wrecked 407, and I can assure it was'nt a pleasant site. The tail rotor hit the boom in flight, whereafter the boom broke just aft of the horizontal stabilizer, and the vibration that followed, practically tore the boom off. The helicopter went inverted, and crashed in that position with no survivors.

Paco your instructor was pulling your leg when he told you that the 407 has'nt killed anybody, and his nose must have grown a kapola feet when he told you that the 407 flies very well without its tail. It does'nt! Trust me.

When the first 407 crashed, Bell issued some AD's, and crew jokingly called the earlier model 407 the 407AD, coz every week there was an AD to comply with. Bell spent hundreds, if not millions of man hours trying to find a solution to the problem. They issued all sorts of AD's. No abrupt pedal movements above a certain speed. They limited the VNE etc. Then told the 407 owners all is cool, nothing wrong with your heli. And now????
What are they going to say now? Had this incident occurred in flight, I'm sure the pilot and the occupents would not have lived to tell the tale, and other pilots would probably have just said "yeah, the guy was a freshman, and he did'nt know what he was doing. He probably did something he was'nt supposed to do".

It sucks!
407 pilots, beware.

correct me if im wrong but wasnt the 407 developed from the OH 58 KIOWA WARRIOR? similar design...has the military had any problems with the tail rotor on the 58 warrior?

didnt the A STAR have initial problems with tail rotors hitting the boom and they extended the drive shaft?.....just a faint recolection of mine..anyone care to elaborate.

As one of the people involved at Transport Canada when this happened, perhaps I can shed some light on this.
Unless there has been something else happen to the tail rotor since 'the fixes' were put in, there were only three incidents of tail rotor being chopped off. In all three cases, the pilot was able to land the helicopter, and the only fatalities were in the last one in South America, where the passengers exited the aircraft with the rotor still turning and were hit by the main rotor blades.
Perhaps there has been something else happen since then.
There was one other incident that was thought to be a possible tail rotor strike, in the Gulf of Mexico, but it was later determined that the pilot had had a fatal heart attack- the damage to the tail boom was not consistent with a tail rotor strike on the boom.
The fix was an 'active' tail rotor stop that came in when the airspeed went above 50 KIAS and retracted at about the same speed.
This latest incident sounds like something similar, and it's going to be interesting to see what happens.

As for similarities to the OH-58D - yes, it has the same tail rotor, but the OH-58D can't go anywhere near as fast as the 407, and that appeared to be part of the problem- hence the airspeed restrictions that were put in place until the fix was sorted out.
Hope this helps to clarify things.

Mr Selfish, the problems that Paco mentioned with the 350 in Canada are not the typical "Jack stall" that we have all heard about.
This seems to be a cold weather situation, where high time pilots have lost control of the aircraft.
Please don't "try harder" to attempt this yourself, as I doubt that you have the required low temperatures, and your family won't like the results !

I have several thousand hours of Squirrel time and have encountered "Jack Stall" or as EC describes it..."servo control transparency". Let me be the first to warn you, you need not "try" to enter this situation, it happens at the most inopportune moment and it hits hard. I was in a B model at 4000 lb AUW circling a fire at 4,000 with a gentle 15 degrees of bank and the controls simply froze.
Be very aware of this situation, and never allow yourself to enter a situation where a hard turn or climb is required for safety, as that's when it may happen. Remember, the only way to exit this "transparecy" is to reduce collective and bank angle.

-----------

Francois, I too am mis-informed over the number and seriousness of 407 Tailboom problems worldwide. AS with Paco, we probably only get Canada and USA info via the NTSB website and I was under the impression, that the majority of accidents were not fatal. In one of the Tailboom accidents, the aircraft was landed safely and the only fatalities were 2 passengers running away uphill ( Brazil?)
Do you have an accident website or database that you access (in SA?)

------------

Belly Tank, you must be almost as old as me, I too recall that situation when Astars first hit the skies in the late 70's. The flexible blade-spar allowed the T/R to contact the boom, and the fix was a longer shaft on the T/R gearbox output.

Further to my last - normally reliable sources tell me that the most recent South African incident happened on shutdown in very strong winds. Completely different situation than the previous incidents/accidents.
If I hear more, I'll pass it on.

Story is the 407 involved in this incident (ZS-RLS) was on the ground parked with the wind at between 20 to 25 knots at an angle of around 3 to 5 degrees on the right of the nose. The aircraft was shutting down and with the rotor speed at around 42 odd percent, there were half a dozen or so knocks which was the tail rotor hitting the tail. Initial suspicion was that the pilot had put peddles is to reduce the rotor speed but after questioning, it was discovered that the rudders were level.

Where could the problem lie?
What caused this?

No-one has any answers yet! Just a whole lot of shoulder shrugging and confused expressions.

Dynamic, you sound "close" to the scene, did the T/R deflection pinch that "tell-tale" 1/8th inch gap on the sides of the T/R Hub ?

Randy Bechtel did my conversion, and he strikes me as a guy that knows what he's talking about, especially as he used to be Bell's Chief Instructor.

Mr Selfish - these hardovers are not transparency - they are a sudden uncommanded movement of the cyclic to one side, uncontrollable even by big beefy guys who regularly bench press 180 lbs. We had one on the ground where I was working last Summer (nothing to do with cold weather), there were several others reported and one not reported (shame on the very large company involved). It is entirely possible this condition was responsible for the deaths of one or two highly experienced pilots. I believe there have been 9 or so incidents, and the machine was not far off being grounded - in fact I believe Ontario MNR did just that.

There have been some thoughts that it could be water getting into the hydraulic fluid, and creating an ineffective mush, even though both fluids by themselves would do the job. However, that doesn't explain the hardover - the current opinion is that the accumulators aren't dumping at the same time, or rather one may be dumping and the others not. Who knows? I know that I don't plan to fly one until it's sorted, hence my contribution in the other thread about giving it all up for the risk (but never say never!!).

Then again, the jetbox used to be a killer, and now it's officially the safest single-engined aircraft, including fixed wing.

Phil

1/8th inch gap on the sides of the T/R Hub
 

407 Driver - Nope. The gaps have not moved or bent closed at all!!!

Hmmm, now that's interesting.....!

Agusta are planning on a fenestron design so perhaps there is a colaboration going on with Bell

"...and second by maturing key technologies in service ..."

Is that another way of saying that they'll be using their customers as Test Pilots ?

Bell Publishes information letter regarding 407
 

There was a thread posted here on a Bell 407 based in Cape Town South Africa that was recently involved in an incident whereby the tail rotor contacted the tailboom during shutdown in gusty conditions.

The SACAA viewed this incident in a serious light, but Bell did'nt. As expected, they blamed the pilot and issued an Information Letter (IL 206L-04-75) dated April 05, 2004 whereby they stress the importance of adhering to the shutdown procedures in the 407 Manual.

What Bell is saying that the pilot did not have the collective in the full down position, neither did he have the pedals and the cyclic centered. Now this is utter bullsh1t! The pilot is a pro, and followed the shutdown procedure impeccably.

What Bell is neglecting to tell us, is that their 407 is riddled with problems, but its the usual old story, "one upmanship". Had the incident occurred in flight and the tail boom maybe seperated from the rest of the frame, the occupants would have been statistics, and the pilot would more than likely have been blamed, as usual.

Shame on you Bell!:mad:

With a little time in the 407 I always thought it was going to be a nice machine. The Motto I always carry is "Never fly an A model of anything" it most certainly applies to the 407.
I met one of the 407 drivers in SA who had one of the failures a year or so ago. He was not thrilled with it for sure. By the comments here it appears the T/R has the ability to touch the tailboom under certain conditions. To me thats a No No......pedal stops or not.

Clipboard stated (Re: 407 tailbooms) "the occupants would have been statistics" . I suggest that you read the whole thread, I recall that a reliable source posted that there have been NO fatalities related to the tailboom issues with 407's. You mention that this pilot in question is a true professional ( I believe you), so I'm sure that he would react with his experience and manage a tailboom loss ...as the other pilots encountering it have done.

Personally, my tail boom has not fallen off yet, (my mechs have found a crack once) and I like the aircraft, so rather than whining about it, perhaps you should buy a superior EC product...they NEVER have problems I've heard ?? or perhaps ask the ENG pilot in NYC last week for his opinion :D