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Nor did I imply such, Sultan.
The John Lovell quote re significant rotor speed droop, with no indication of what " significant " means in this instance, naturally provokes thought about what can cause that. My post 29 had a few thoughts about that. What I can add from experience is that cutting one engine from a two engine condition at the higher helicopter speeds, and under the assumption it is done in a controlled incremental build-up manner, shouldn't result in an Nr droop that would be abnormal. The speeds you mentioned, I.e., the 200 kt range, would be a dive point, hands on controls, with normal pilot reaction time. But as I wrote earlier, the information provided publicly to date does not allow the formation of any hypothesis that is defensible. As to SA ( and I guess as a retiree that includes me ) reading Part 29 re the 30 min dry run Reg's , please check your PM's. |
JD
I have heard of a number of 60's that ECU lockout checks on one engine resulted in damage to or loss of the aircraft. The highest visibility one was the HMX-1 ship. So the prescident has been established of unintended consequences when testing engine failure modes and those made it to the presidential fleet. Report still remains doing engine out (one) testing at extreme of the airspeed range rpm was lost resulting in loss of the aircraft. As to what the crew felt or perceived prior to the event is still being analyzed. The Sultan |
Lone....gratuitous caustic comments elicit the same.
Just being a mirror. |
The Sultan:
Precedent. The matter of the S-70 / H-60 ECU lockout, and the hazards thereof for the unwary (with which I am familiar) may be worthy of its own thread. It doesn't belong in this conversation. John D is not trying to start a Bell V Sikorsky thing, and quite frankly I think I speak for all of us when I say none of us participating in this thread wants to go there. This crash, this loss, where the state of the art of rotary wing aviation was in the process of being advanced (and it cost our industry two fine men) is of interest to a great many regardless of favorite model or favorite manufacturer. |
Lonewolf, well said!
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Quote: Originally Posted by 212man View Post Yes AEO is - I wrote AEI. You can go back and edit your post to reflect the correct term so that what you wrote fits what you meant to write. (Heh, I just edited that last word since I wrote "wrote" instead of "write" and missed it the first time. Super example, eh?) @TheSultan: John D has been sharing in good faith ... I'd encourage all of us to do likewise. @SASless: winding up Sultan? Let's keep it classy. Last edited by Lonewolf_50; 27th Jul 2016 at 23:13. Reason: typing spazz Lonewolf_50 is offline Report Post |
Originally Posted by 212man
(Post 9454680)
Or you could just read more carefully next time! If you look at the bottom of your post it says 'edited' (as all edited posts do) - mine does not and is original!
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"Bell 525 Relentless broke up in mid-flight, NTSB says"
Bell 525 Relentless broke up in mid-flight, NTSB says | The Star-Telegram |
NTSB states blade strikes on nose and tailboom
https://www.flightglobal.com/news/ar...ed-bel-428027/
Main rotorblades struck nose and tail of crashed Bell 525, says NTSB 01 AUGUST, 2016 BY: DOMINIC PERRY LONDON Investigators probing the fatal crash on 6 July of the first Bell 525 Relentless prototype believe the main rotorblades struck both its nose and tail boom as it performed a high-speed simulated engine-out test in Texas. Both experimental test pilots died in the accident which took place as the super-medium twin approached its never-exceed (Vne) speed. The tracking website FlightRadar24 suggests the Relentless was travelling at about 200kt (370km/h) at the time of the crash. Confirming quotes originally reported on theRotor & Wingnews website, officials from the US National Transportation Safety Board (NTSB) say they saw signs consistent with blade strikes to the nose and tail boom of the 525 during simulated one-engine-inoperative trials. Data from the helicopter indicates that main rotor RPM had also fallen significantly, the NTSB says, with some of its five composite main rotorblades appearing to drop from their normal plane. However, the agency declines to speculate on any potential cause. “We have a great deal more work to do until we get into the analysis phase of the investigation where we will put all the data together to hone in on the factors that contributed to the crash,” it says. The GE Aviation CT7-powered helicopter subsequently broke up and crashed around 30nm (56km) south of Bell’s facility in Arlington, Texas. Although the majority of the wreckage was consumed by a post-crash fire, the 525’s flight-data recorder was recovered and data successfully downloaded, the NTSB says. Bell declines to comment on the NTSB statements. Flight tests using the remaining two prototypes of the fly-by-wire rotorcraft remain suspended, although the company continues to perform ground-based certification work. |
Some additional insight into the aircraft's airspeed at the time of the accident, from NTSB: Bell 525 suffered main blade strikes
Flightradar24 shows the last data point for FTV1 was at 1,975 feet at a groundspeed of 199 knots. At the time, it was tracking south to north with a 20-knot tailwind, equating to an approximate airspeed of 179 knots. |
Ian, near the bottom of that article is the following:
The accident investigation will include copious data from real-time telemetry associated with the flight-test process, as well as the crew observations and video recordings from the chase helicopter, a Bell 429. |
Lone,
Granted, and I don't usually post on accident threads (preferring to wait for the official report), but the tailwind 'information' quoted in the AIN article hadn't been posted before, and I figured it might help resolve the debate over IAS vs. TAS vs. GS, etc. Cheers, I/C |
Hello to all,
I'm quite a neophyte on this thread but as I read it many times, It appears that some (not all) of the blades had left their track. I'm wondering how it can be possible without considering the integrity of the pitch rods ? Maybe I'm wrong but It's quite unusual to see blades living their life independtly each other... |
Originally Posted by Tatischeff
(Post 9475125)
Hello to all,
I'm quite a neophyte on this thread but as I read it many times, It appears that some (not all) of the blades had left their track. I'm wondering how it can be possible without considering the integrity of the pitch rods ? Maybe I'm wrong but It's quite unusual to see blades living their life independtly each other... skadi |
Originally Posted by Tatischeff
(Post 9475125)
I'm quite a neophyte on this thread but as I read it many times, It appears that some (not all) of the blades had left their track.
So far I did not understand it that way. The signs so far rather seem to point to a Retreating Blade Stall and resulting blowback of the entire Rotor disc. Maybe I overlooked something. |
[the NTSB says] some of its five composite main rotorblades appearing to drop from their normal plane. It could be a misunderstanding from the journalist but when NTSB says "some", I'm pretty sure It does not mean "all". @henra : What you say is interesting: a retreating blade stall can result in the rollback of the entire rotor ? So the maximal loss of lift is on the back of the H/C (the phase shift is still applicable) ? |
Originally Posted by Tatischeff
(Post 9476221)
@henra : What you say is interesting: a retreating blade stall can result in the rollback of the entire rotor ? So the maximal loss of lift is on the back of the H/C (the phase shift is still applicable) ?
A severe retreating blade stall usually is a reliable way to surgically chop off the tail of any helicopter. Teetering Rotor systems are significantly more prone to it but in a very violent case you will achieve this even in a fully articulated system. The only type of rotor system where it might be more or less impossible would be a rigid head (Bo105/EC135). I'm not aware of a case where someone managed to chop off the tail in one of those with a retreating blade stall. |
henra,
Didn't the NTSB say it hit the nose and tail? |
Originally Posted by CertGuy
(Post 9477691)
henra,
Didn't the NTSB say it hit the nose and tail? |
In 1981 in Oz, a B-model Huey had a mast bump and blade separation. One blade entered the cockpit on the left side, killed the left-seater, sliced off the left cabin door and the long-range fuel tanks on their mount and still had enough energy to take off the tailboom too.
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