U.S. Marine Corps AH-1Z Zulu
 

Congratulations to the United States Marine Corps helicopter flight crews for fifteen years (5475 days) of mishap / accident free operation of their AH-1Z Viper Helo with original design main rotor. :D


First Flight: 10 December 2000


Reported Accidents: 0


Main Rotor Redesigns: One (1) initiated & worked on for approximately ten years. Zero completed, implemented or incorporated. :=



OORAH!, MerryChristmas and Happy New Year.

Hello Otterotor,


You mean that the Marines are operating the AH1Z for 15 years ? I thought that it was much less than that.

That's a noteworthy operational record, and is very nice work by those who designed, built, fly and maintain these helicopters. (@Helihenri IOC was in February of 2011, FWIW).

To put into perspective how impressive that safety record is, I'll dig into my memory and present the following (any errors in recall are apologized for up front):

1. From 1982 to 1986 Navy SH-2F: 14 Class A mishaps. (Over a dozen folks were lost :{
2. From 1989-1993 three SH-60B (a mature aircraft at that point) class A Mishaps in the West Coast wing. All of them included people I knew personally. (Four fatalities: two TRGB failures flight over water, one uncontained engine failure led to losing the second engine, flight overwater). If there were other Class A's or losses in Seahawks during that period my memory is failing.

This may not be an apples to apples comparison, as it's a fixed wing training aircraft that flew a boat load of hours, but it covers a similar period of time ...
3. During the period from 2000 to 2013, the T-34C (a very mature aircraft at that point) had seven class A mishaps and 8 fatalities. (I think I have accounted for them all). During that period, the T-6 began to replace the T-34C and it was completely replaced by 2013. That makes it an inverse of the look that Otterotor's gives us of flying the Viper "from birth into adulthood."

H - H
H-1 Upgrade contract let in November 1996. Clean sheet rotor design initiated. Zulu first flight Dec 2000 with Bell flight crew. Flight testing with Marine pilots initiated 2002. First delivery 2006. Zulu IOC 2011 due to Target Sight System development issues. All info from memory, if it serves me properly. Otter

Thanks to you both :)

Not mishap free...
 

It is not true to say there have been 15 years of operation on the new four bladed flex beam rotor without mishap... There was an in-flight static failure of a rotor blade cuff in 2005 that led to a hard landing and operating envelope restrictions.

There are a few public references to this event on the web.

Was that classified as a mishap or a test/development learning point? :confused: (In other words, was NAVSAFECEN involved in the after action report)?

Marines AH-1Z Zulu
 

Congratulations to the United States Marine Corp helicopter flight crews for sixteen years (5840 days) of mishap / accident free operation of their AH-1Z Viper Helo with original design main and tail rotors.
Was there an event back in 2005? Yes, at flight test over Leonardtown, Md. The data point was intended to be the 1.11 Vne (222 KCAS) and 3.5 G's symmetrical pullup. The recorded data shows 3.7 G's and 223 KCAS. All four cuffs contacted their respective upstops which resulted in compressive buckling failure of each cuff (which was the predicted failure mode). The aircraft (it is not an airplane) subsequently landed with high vibes as the cuffs were no longer as stiff torsionally as they were designed to be. So, a shaky landing on the local golf course but aircraft and personnel survived, I talked with them and visually inspected the cuffs. The data point was slightly outside the design envelope and well outside the operating envelope. It did not go down on my personal log as an accident.


First Flight: 10 December 2000, Reported Accidents: 0
Main Rotor Redesigns: One (1) initiated & pursued for approximately ten years (and $80 mil) with no results to show for it. Zero redesigns completed, implemented or incorporated.


OORAH! Merry Christmas and Happy New Year!

@SplineDrive: how is an inflight event a static failure? The rotor head, as described by Otterrotor, would have been under dynamic loads at the time.

Have a question for you, Otterotor, but before asking it, congratulations to al of the people involved in attaining that safety record, at Bell and the USMC.

Question: re the maneuver described in post #8, it sounds like part of the structural demonstration, and if so, have the test requirements changed that substantially? Mil-D-23222a used to require a symmetrical pullout to limit Nz ( 3.5 for military helicopters ) at speeds up to Vlimit. The language used in the post, I.e., 1.11 Vne, sounds like FAA Pt 29 lingo. Just curious as to the test requirement.

Thanks,
John

Lonewolf; A single load failure event (or very low cycle count) is described as being a 'static' failure vs. high cycle count and gradual failure as evidenced by fatigue striations as being a 'fatigue' failure.


JohnDixson: Good question, I was not up to speed on the origin of the flight card and thus the requirement. I was informed that the G's occurred during symmetrical pull up at 1.11 Vne. We would have been governed by Marine Corps or NAVAIR requirements but I am not familiar with the details of those requirements. At the time of the event I was lead design engineer at the flight test site (PAX) maintaining production configuration for the five (5) flight test aircraft (which, except for Z-1, which had the older cockpit dial indicators vs. digital, we later DD-250'ed to the Marin Corps customer as production aircraft). The reason I was called on to inspect the rotor was my previous position as lead structural design engineer on main and tail rotors.

@Otterotor: thanks for the terminology clarification.


@SplineDrive: now I understand why you put it that way.

Quite simply really. They weren't ordered to crash. :)

AH-1Z first flight anniversary
 

In my opinion:
Congratulations are in order to the United States Marine Corps helicopter flight crews for seventeen years (6205 + 4 leap year days = 6209 days) of mishap / accident free operation of their AH-1Z Viper Helo with original design main rotor (identical part numbers fly on UH-1Y Venom).

First Flight 7 December2000, Reported Accidents: 0

Original design initiated November 1996, clean sheet, rotor components designed (including main rotor yoke, cuff, blade, mast, rotating controls, main transmission, tail rotor driveshafts, intermediate gearbox, ninety degree gearbox, tail rotor rotating controls, tail rotor mast, tail rotor hub and blades), parts fabricated,fatigue test machines designed and fabricated along with composite tooling designed and fabricated (unique thick laminate technology), one or two of each main component fatigue tested, aircraft assembled and flown, all in approx.four years. No prototypes, 4 of the 5 test aircraft were DD-250’d (delivered, four of five test aircraft self-deployed simultaneously East Coast to West Coast USA at termination of Flight Test effort, 8:00 A.M. May 9th 2006) to the customer as production aircraft, with the fifth being shot up in live fire testing on west coast.

Main Rotor Hub Redesigns: one (1) initiated & pursued by OEM Bell Helicopter for approximately ten years (2002 to 2012) (and $80 mil) with no results to show for it. Zero redesigns completed, implemented or incorporated.
The Marine Corps has more-than-made-up the loss of approximately $80 million spent on the unproductive (0.00 results) effort to redesign the H-1 Upgrade main rotor with financial returns on the unused pre-determined & assigned airframe attrition rate of 1.00% per annum for the AH-1Z Viper (@ approximately$26 million / copy).

OORAH! Merry Christmas and Happy New Year!:O

Congrats are in order. J thru Z and kept the round canopy the entire time! (not going to count the G's cause they were loaners)

AH-1Z first flight anniversary
 

H-1 Upgrade Fatigue Life Summary

Approximately 90% of main rotor components have been assigned 10,000 Hr. fatigue lives. The predominate vibration source for main rotor fatigue life limits is (approximately) the number of blades per revolution or 4/rev.
100% Nr for H-1 Upgrades = 296 RPM.
The calculation for predominate cycle count for H-1 main rotor components:

4/rev x 296 rev/min x 60 min/hr x 10,000 hr/life = 710 million cycles / one life time

Or 7 x the accepted cycle count of 100 million cycles for infinite life.
This implies that the components assigned a 10,000 hr. life are being subjected to oscillatory and associated steady load combinations below the endurance limit of the component and therefore the component will not fail due to fatigue loading.

Additional H-1 Upgrade Percentages

1) Greater than 100% increase in fatigue lives for many rotor components (compared with AH-1W).

2) Rotor & Drive train components are 100% interchangeable between Gunship AH-1Z and Troop Transport UH-1Y.

3) 84% of all helicopter components are common between Yankee & Zulu.

4) Installation of Bearingless Main Rotor has reduced parts count from a standard articulated rotor by 75%.

5) Installation of Bearingless Main Rotor has reduced overall vibratory levels by 70% from AH-1W levels, contributing to extended electronic equipment life. (life expectancy not-yet-quantified). The composite material (thick laminate fiberglass) used for the bearingless main rotor prevents corrosion from degrading those components, assisting with the overall durability of the rotor in service.

6) The only lubricated component in the main / tail rotor hubs/blades/controls is the main rotor swashplate bearing. Basically one installs new upgrade main and tail rotors on a new airframe and flies with the only replacement items being elastomeric main rotor shear restraints (qty 4), elastomeric / liquid dampers (qty 8), lubricate (grease) (1) swashplate bearing and replace tail rotor elastomeric flapping bearings (set of 4).

7) Page 4-9 Flt. Man. VNE = 200 KIAS. Stable flight demonstrated 223 KCAS in slight dive with symmetrical pull-up.

8) Original sized gonads proven to be adequate, thus no requirement for AH-64 Apache’s modified main rotor “Mega Nuts” (joke).

Congratulations are in order to the men and women of the United States Marine Corps who fly and maintain the H-1 Upgrade aircraft

AH-1Z’s 07 December 2018, 18th anniversary of first flight: 6574 days with zero incidents.

The four events that I am aware of (public data) are as follows:

1. 20 Jan 2017, engine warning light, precautionary night landing, Ikei Okinawa, Japan, instrumentation.
2. 8 Jan 2018, 4:45 P.M. local, T/R warning light, precautionary landing, Okinawa, Japan, wiring issue.
3. 23 Jan 2018, 8:00 P.M. local, warning light, precautionary landing, Tonaki Is., Okinawa, Japan, instrumentation.
4. 1 June 2018, low oil pressure warning light, precautionary landing, Fallbrook Airpark, N.E. San Diego, instrumentation.

Merry Christmas and Happy New Year OOH – RAH!

Otter:
Are there more FMS orders pending?

Lonewolf,

As I understand, the current FMS interest is:

Pakistan's 15 Zulus are on hold ... not delivered and not certain they ever will be.
Bahrain ordered 12 Zulus.
Other countries interested in Y's and Z's but no orders.
Japan interested in replacing older AH-1S cobras, no orders.

Romania issued a letter of request for 21 Venom and 24 Vipers over the summer

2 fatalities in U.S. Marine Corps Zulu crash at Yuma, Az.
 

https://www.marines.mil/News/Press-R...ructor-course/

Thoughts and prayers go out to pilot's and copilot's family and friends.

Crash under investigation. Otter