Engine cut-offs in combat

Canadian (MAAC) combat rules require a functional fuel cut-off for fast combat but not for slow or 1/2A events.

Can anyone explain why the cut-off is mandatory only for the one class? Also are the rules similar in the USA?

Thanks, Eggy

The AMA has a rule that if it goes faster than 75? mph it has to have a shutoff. Does not apply to FAI of course.

I'll tell you my opinion.

Combat planes sometime get cut loose and fly away. They can hit people and things. For example, a guy got hit in the face with a combat plane in Seattle in 1970, resulting in the Navy dropping its sponsorship of a big, annual contest and a disaster for control line activity in the Northwest. We accepted this peril as a part of the sport. Responsible combat contest organizers held contests in the boondocks and didn't advertise them to the public. Several years ago, John Thompson, to keep a contest site at the Eugene, Oregon airport, started requiring engine shutoffs at combat contests there. We grumbled, but people figured out how to make shutoffs work. We began to like them because they saved our airplanes as well as their targets. Responsible contest directors liked shutoffs, too, because they reduced their liability for accidents. Many CDs started requiring shutoffs, and the AMA passed a rule requiring them.

Unlike now, in those days there were no good, commercially available engine shutoffs. There existed then a group of people who were daunted by the complexity of making their own shutoffs. Pretty much the same population dropped out of AMA ("fast") combat at the last escalation in engine technology. They convinced the AMA contest board that certain girlier variants of combat are safe enough to be exempted from the shutoff requirement. I presume the Royal Canadian combat authorities accepted the US rules without much independent review, as Dan would have Canadians do with all matters.

Thanks for the insight Howard. This pretty much confirms what I need to present to my club. That's why I asked.

As "Shutoff Inspection Officer" for two "Bladder Grabber's", my take is that all shutoffs so far require a fair amount of line tension to function (stay "on"). It seems to me that D-Bat would have trouble with generating enough line tension, and probably most 1/2A's. The 75/80 MPH SLC models should manage alright.

Jeff Rein, after nearly being decapitated by an F2D, which hit his model box and destroyed 8 models instead, went on a shutoff jihad. He made shutoffs for every airplane size. He set out to win every combat event using a shutoff in every match. He won 1/2A at the NW Regionals using shutoffs. Now he and Tony Huber are offering his NC-machined bellcrank shutoffs for sale. I'm slowly retrofitting my Mejzlik fleet with them.

I don't think you'd need shutoffs for D-bat. The smell pretty much clears the venue of personnel.

>
>I don't think you'd need shutoffs for D-bat. The smell
>pretty much clears the venue of personnel.

Actually, the throbbing powerhouse PAW 2.5cc "Dismals" generally stop when they hit a line. Sometimes the streamer string does the job. But it is very cool combat...average people can watch/fly it and see what's going on, the airplane bounce, and usually one pit crew or the other will get the model restarted and back in the air. They're more interested in flying/watching a good combat match than who wins. Bob Carver had a huge grin during his matches, but he also was seen to stay away from the stinky end of the lines. Steve

On the other hand, the lack of line tension also means that you don't NEED the extra spring tension that is used to overcome the weight of dragged lines in the case of a line cut near the handle, so you could build the shutoff with much lighter springs.

Hi Howard, you may recall our discussion re 777/Impact balance tabs at the Nats last year-anyway, I'm affirming your opinion pertaining to shut-offs. I didn't know of a precedent such as the one you mentioned in combat. Carrier has had an accident, and jet speed has come very close. Once our flying fields were in remote areas but just like real airports, people start moving in. Soon the fields are surrounded by soccer fields. One C/L plane ripping into a crowd of bystanders, jet, half A, whatever, and we're facing litigation and tough sledding in general- AMA insurance notwithstanding. Locally we always use the jet safety nets and I hope shutoffs on combat ships would become SOP. It's not just the CDs, we all should promote/take advantage of any safety developments to preserve what we're doing. Not paranoid- just thinking ahead! Here's wishing all a safe 2004!!Respectfully submitted, dale g

I missed the shut-off revolution in Combat, as just about the time they became widespread here in the NW I merrily skipped and froliced over to the Stunt circles.

However, I am against their use.

Used to be if one had a real good fly-away all you lost was a Fox 36 and an airplane, in exchange being presented with another terrific Combat story, one which could be embellished over the years. A fair trade, in my opinion.

Today if cut loose you lose a $50.00 model, a $300.00 Nelsoni and the darned shut-off. No story is good enough to make that a fair trade.

It is a way of culling the substandard shutoffs.

Take a little closer look at the history. The shutoff rule in Fast combat was put in as a partial fix for a serious safety problem. A 1.5 lb. plane going 120 mph can be lethal.

Once a rule was in the works some people took a closer look at the rules and realized that requiring shutoffs across the board would mean that they would be required in every combat flight. You would no longer be able to put your Shoestring up against your buddy's Flite Streak in a friendly fun match. The actual rules are a bit vague, but the Safety Code falls back on the rulebook, so if shutoffs are in the book, they would probably be needed to comply with the safety code. Since folks have been flying combat at slower speeds since the event began with very few safety problems it seemed reasonable to exempt slower sport planes from a rule designed to cope with a much different problem.

The exemption is not just for the occasional Ringmaster match. It applies to contests, too. It's just irresponsible.

>Take a little closer look at the history. The shutoff rule
>in Fast combat was put in as a partial fix for a serious
>safety problem. A 1.5 lb. plane going 120 mph can be
>lethal.

I certainly don't want to shock Mr. Ferocious, but at the '02 BG, when a certain combat model impacted over by the Snohomish Municipal Airport runway (and actually on the active grass runway), I'd bet money that it was MUCH closer to 200 mph. Not long before that match, I expressed some concerns about the leadout/ line attachment method used on that particular model. It was impressive, winding down from about 500', Nelsoni howling. Steve

PS: The shutoff worked on the ground, but aero loads prevented it from working in the air at high speed. I'd like to see some regs on shutoff design.

>I certainly don't want to shock Mr. Ferocious, but at the
>'02 BG, when a certain combat model impacted over by the
>Snohomish Municipal Airport runway (and actually on the
>active grass runway), I'd bet money that it was MUCH closer
>to 200 mph.

Faster than 160 mph? Perhaps if it was missing both wings.

I worry about flyaways and the inability of even a
properly functioning, instant acting shutoff to stop the plane.
When I (or my computer) does the math, the plane doesn't
always slow down very fast. Indeed, if the lines are
cut at the plane, it will accelerate quickly until the
engine stops. Luckily, the lines usually break while
the plane is manouvering violently, so it won't be
running at top speed. In any case, a plane flying directly
into a spectator or judge (for instance) will hurt
him badly.

That's not to say shutoffs are useless. They are quite useful.
In particular, they help avoid the case Steve describes,
where the plane flies up and away, then screams back into the
ground 1/2 mile away.

Howard and I have pondered ways to have the shutoff
yank the elevator to full up/down, which would tend to bleed
off speed very quickly and confine the plane's uncontrolled
antics to a relatively small space. The difficulty is avoiding
the elevator-yank during a normal landing!

>PS: The shutoff worked on the ground, but aero loads
>prevented it from working in the air at high speed. I'd like
>to see some regs on shutoff design.

Some CDs will not allow certain kinds of shutoff. Seems smart.
I'd sure hate to see innovation in this area prohibited.

As one of the people who, as Howard mentioned, sort of got this shutoff thing started, I still sincerely hope to see every combat pilot in contests using shutoffs that really work. We are approaching that point but haven't reached it yet.
Lack of reliable shutoffs is a part of the reason that I have not flown fast combat since 2000, breaking a 22-year string of activity in that event. (There are other reasons, too, of course.). In the next-to-last contest I participated in, the '02 Bladder Grabber, a flyaway landed in a styrofoam box inside the canopy where my wife was sitting, watching the match. The plane landed literally inches from her. What is interesting is that she was WATCHING the match and did not fully realize the plane was coming at her until its wreckage was in the box. This plane was used by one of the combat fliers who is a strong supporter of good shutoffs.
I've ducked lots of close calls myself, but it was unnerving to have the almost-victim be a loved one. There are always wives, kids and bystanders at these contests, many of whom have no idea what might happen.
Shutoffs do work much of the time, and have made the event much safer than it once was, as I and others have demonstrated. But further development is needed, and I think Jeff's new design is getting really close to what we're looking for. Not to be a "safety Nazi" as I was once called, but I think the day may eventually come when we set some standards for shutoffs, to assure that they will work in the air as well as on the ground.
The time to do this, of course, is after we've really determined for sure what works all the time, not just sometimes.
Like everyone else, I would rather not deal with the hassle, but we have to be responsible citizens if we're going to expect people to let us fly this event in public. I would not fly a combat match without a shutoff on anything other than a half-A.
--jt

Can we see some discussion of some of the more reliable shutoff setups that are being used or can be purchased and sources of these devices. I think more people would use them if they were aware of how they work and where these devices can be obtained at reasonable cost. I am interested in shutoffs that would be suitable for Speed Limit Combat (75 to 80 mph).....TD

See http://www.clcombat.info/shutoffs.html
Note all the subpages listed over in the left column.
I've been using "Roy Glen's Shutoff" but plan to start using
the "H & R Shutoff" (Rein's design). It's very similar to
Bobby Mear's design. Other good ones include Mark Rudner's
scheme and the one sold by Bill Maywald.

Some of these are for sale (see the web page).
All of them are suitable for 80mph.

Combat Guy

Just a couple of things . First I'm not against shutoffs in fast .Used them never had to need one (thank goodness).We up here in the land of the frozen tundra had the shutoff rule 4 or 5 years before the AMA mandate came into effect .This caused fast to be wiped out from that time forward - not one contest since the rule introduction.Two main reasons this happened.First most Canadians fly F2D and second at the time shutoffs were very crude and unrealiable. Had we waited until the US.rule change things might of been different .