Xantos

Hi Guys,
I've been flying a BVM Bobcat since 2005 which has over 300+ flights now.
Ofcourse its seen its share of normal dings etc suffered a few bad landings , bounced down the runway etc.
Its also seen various power plants from 14.5 lbs thrust to its current 30 lb Jet Central Cheetah.
It recently went thru a complete refit , new servos ,linkages , receiver, batts etc when I changed to the more powerful Cheetah.
Needless to say this airplane has always been flown hard and well over BVMs recommended limits for the airframe .
I haven't seen any stress cracks etc either on the booms or wings etc , structurally everything is exactly like it was brand new.
So the question , is there anyway to evaluate the structural integrity of the airframe ?

Dave Wilshere

Nandan

Cracks in surface or visable structure. My BobCat is 8-9 years old and although its not done much flying this year its had a lot and I'd have no worries flying it for years to come. Wings and Fuselage on the BC Composite are immensely strong, I'd go so far as to say over engineered! Though knowing some people had 160SX's in them maybe I can see why. The booms are the only weak point, from the rear tube to the TE of the wing is under the biggest load. Flight loads are one thing, but landing shocks, transport with craddles under the front fuse and mid/rear booms are another hazzard (as seen on the early KC boom issue)
BVM are great for watching their airframes, there are BC C around with way more flying than yours, Ginger in England has one I supplied him around the time I got mine and that has hundreds and hundreds of "giving death" flights as he has no throttle control ;-)

Basically, look for tell tale signs of stress cracks in the surface finish, movement in fixings (booms need to have NO up or down movement in tubes) Any movement will shock the airframe and increase the load given.

Dave

Xantos

Dave,
Agree with you -BVs quality is great !!
Just makes me wonder how much stupidity an airframe will take every time I pull out of a full power dive

Jim Cattanach

I recently sold my Avonds F15. It had somewhere around 2,300 flights & was still airworthy.
It was my main Saturday & Sunday jet for many years. Turbines varied from Wren 54 with 14lbs thrust, to Merlin 140. Around six different ones.
I changed the original u/c for Jet Legend ones, fitted two sets of u/c formers & one thrust pipe,
It had four different colour schemes in its life with me.

murdock0700

If it's an FEJ airplane I would say, Before you ever take it out of the box...

M.

basimpsn

My Feedback: (5)

Lately I'm thinking of retiring my SM F-18C due to my big block turbine. From 750, 1000, Rhino, kingtech and now it's getting hard to see with the Blue Angel scheme.

Kevin_W

My Feedback: (1)

My Bobcat XL is 12 years old and has upwards of 1400 flights on it. Most of those flight included high G turns, snap rolls, spins, and other maneuvers that are less than gentle on an airframe. It has also experienced an unknown number of wing tip scrapes, a couple of gear up landings, and had the entire nose section (from the canopy forward) replaced due to a mistake while trying to spot land with it (thanks Vernon ).
Over the years I have periodically gone through it and inspected the integrity of the airframe and all the systems. Other than the wing tip scrapes (and the nose that one time), the only repairs I have had to make were to some spanwise stress crack in the inner wing panel around the fuel tank bays. I think the weight of the fuel tanks was causing the wing to flex during high G's. They have not re-appeared in the last couple of years, so I think I fixed that issue.
I keep a close watch for any new issues, and I will continue to periodically take it apart and inspect things, but I am not at all worried about the integrity of this airplane. I will continue to fly it until I either get tired of it, or make a catastrophic mistake.

mr_matt

My Feedback: (10)

I think a tougher question is when to replace the servos. I have a plane with 1000+ flights. I made it so I can take off the flight controls to check the hinges and I did some repairs there but overall it is fine. The servos test fine but how long will they last?

dbsonic

My Feedback: (3)

I agree with all that's been said. Check the airframe and formers for cracks. If the bond is good you should be fine. 3000hrs is not uncommon for fiberglass airframes in the full size world with life extension well beyond that, usually in 3000 hr increments.

Matt makes a good point. Electronics may be another matter including basic conductivity issues, oxidation of plugs/extension and wear, and believe it or not dirty switches(mainly if external) with worn contacts and intermittent behavior.

rcjetsaok

My Feedback: (7)

So let me make sure I understand your math... You are saying 3,000 flight hrs. and every 3,000 hrs afterwards to inspect the airframe for any problems ? That equates to every 30,000 flights.... Your kidding right ?? you would have to fly 5 times a day 365 days a year for 16-1/2 years to reach the first inspection !!!.... ( Based on a 6 minute flight ) Man, I love this Hobby as much as the next guy, but I don't think I could do that !!


Danno

dbsonic

My Feedback: (3)

No math just stating a typical airframe life expentancy and extension.

But if we were to translate full size flight hour to our models, I would say to takeoff, fly around and land takes anywhere from 30mins to 1 hour so we are talking 3000 to 6000 flights.

IMO something like a CARF Flash that is such a great flying and landing airplane could hit these numbers and there maybe some out there that already have.

DrScoles

My Feedback: (18)

After reading this, it makes me feel much better about just keeping my UB and bandit for a long time. They are not gonna get the reps you guys are talking about, I was just worried about age. I see some of these planes are more than ten years old and still going strong..awesome.

basimpsn

My Feedback: (5)

That's a tough one... I ask myself the same question about when to change my old Ram 1000 bearning with over 600 flight and no bearing noise

jason

My Feedback: (1)

My composite Bobcat as Dave says is 9 or so years old. I don't keep a log on flights but I'd say about 100 a year would be a fair estimate. It's had a few engines over the years and a servo change was done about 5 years ago and I think it's due again now. I think I'll also do the leads this time too. I feel the airframe is strong as the day I got it.

Jason

Dave Wilshere

Member of the family ;-)

Servos
Most servos are having an easily time in Jets, Flaps and rudder (if you KE a lot) are the only workers. Look at a flights current draw on Jets, its lower than the same flight time on a 6 servo 50cc aerobat. With quality servos (JR) I know of petrol aerobatic aircraft that have done 300 flights on a set of servos and they are beaten to death by vibration and work hard at full throw. Servos can just die, but normally they show signs. slow transit tests are a good one, I load flap and rudder servos before flight to check they hold, or push back. I have always felt there is as much chance of a new servo failing, its why I run in servos and heat cycle them before installation. One of the UF models I built last year had an 8411 die before the first flight, first one in about 1000 servos! but it can happen.
As Jason is saying servos that are plugged in and disconnected each time a model is assembled might wear the pins, so how many times are connections good to be scraped? Depends on the lead quality! Something me and J have in common is a fussy requirement and definite use/not use policy.