Really Stupid Question
 

Can a jet only be flown with pcm or is fm ok.

RE: Really Stupid Question
 

On a purely functional level FM will work fine, but I believe with the AMA you have to have a radio failsafe set to kill the engine as well as the ECU set to kill it. I flew my first turbine jet with an FM receiver for the first little while and never had a problem. I would always choose PCM given the option though.

RE: Really Stupid Question
 

Ok thanks my fadec has a built in failsafe I thought that would be enough. Pcm is no problem just have to buy a pcm rx (tx will do either).

RE: Really Stupid Question
 

I Fly both systems, but I prefer PPM....

and as long my PPM plane is old, flies almost every weekend and it is still in one piece, looks like your question is not stupid..;)

However. i will jump into a 2.4 Ghz system as soon it proves to be reliable...



Enrique

RE: Really Stupid Question
 

FM or PPM is just fine and can be perfectly AMA compliant.

Multiplex/Hitech makes a receiver that utilizes failsafe - Fusion 9/Hitech - can't remember my Multiplex receiver's model number are 2 I can think of. They work with other transmitters as well.

God Luck

RE: Really Stupid Question
 

Really Stupid Question Is the one you don't ask.

RE: Really Stupid Question
 

PPM for me with Multiplex IPD Rx... until I switch to 2.4Ghz.

RE: Really Stupid Question
 

SUSTAINED!!!!!

RE: Really Stupid Question
 

Thanks guys I allready have at least 10 rx all fm and well tested but I have an older airtronics vanguard pcm that works perfectly though. Building a jetmach 60 trainer and don't need a real fancy radio or servos. Nothing wrong with using an older radio when simple will do I quess. Wanted to keep my first jet simple, easyto fly, & cheap. I really like cheap.:D

RE: Really Stupid Question
 

The AMA reg (document 510A) requires all radios to have fail safe. This means PCM is good and PPM if it has an aftermarket failsafe device add-on (if there is such a thing). I've read some time ago about some kind of device that basically gives failsafe functions to a non-PCM receiver, but don't know anymore about it.

RE: Really Stupid Question
 

IPD Rx's have failsafe and work with any FM radio.

RE: Really Stupid Question
 

There are a number of PPM rx that have error checking and failsafe built into them.

H

RE: Really Stupid Question
 

GWS do a failsafe that works fine.

I have flown with Futaba 138 RXs and the GWS FS-1 Failsafe Unit and had no problems.

I personally like having advance notice of a poor link with the model [ i.e. getting glitches] that PPM gives. I find the sudden lockout that PCM gives unsettling.

Some of this comes from a background in RC combat where you have a large number of TXs spread out along a line and interference is an expected event.

RE: Really Stupid Question
 

Eureka!!!! I have been wondering if I'm the only person who hates PCM lockout and prefer a glitch. Much rather have a glitch and land my plane, than get a PCM lockout and crash.

Springbok Flyer

RE: Really Stupid Question
 

I also agree about wanting to 'know' about impending problems by seeing glitches as it happens so I can land immediately and check things out. PCM doesn't give you this early warning, it masks minor problems until the trouble is bad enough to cause lockout and the resulting crash [:o], not good. However, in the US the AMA requires failsafe on the throttle chanel to shutdown the turbine in the event of radio trouble. That's a good thing though, you want the engine to shutdown before a crash not only to help prevent the dreaded post-crash-fire, but also to help minimize damage to the engine (read $). I've only got two PCM's one is in my only turbine plane, the other in an electric heli. I didn't know some PPM receivers have built in failsafes. I'm waiting though on the SpreadSpectrum 2.4 GHz to come out in a 10 chanel fully loaded radio like the 9C or 10S. That's when I'll be buying new radios.

RE: Really Stupid Question
 

Don't forget FMA direct (FS8) and Berg (7p). I think Sombra Labs might have one in the works. FMA and Berg (Castle Creations) are the onlyI know of that have failsafe. Multiplex IPD, I've read complaints about it being lower in resolution, and having a noticable delay vs PPM.

http://www.castlecreations.com/
http://www.fmadirect.com/

You can also get failsafe additions that go between the reciever and the servo for an individual channel, commonly used in glow powered cars. I think there was a setup that went between the receiver and the servos on all channels, allowing one to boost the voltage going into the servos beyond 6 volts, it took the current drain off the reciever, and added a failsafe. Zebra comes to mind... [sm=confused.gif]

About 2.4 Ghz, they're having difficulty deciding on a standard. I read some tests have resulted in interference with other brands. AMA is getting involved.

RE: Really Stupid Question
 

The ama safety code line 9 states that radio and ecu must have failsafe to shutdown engine. Looks like I'll be buying a new rx.

RE: Really Stupid Question
 

If you have an AMT engine you don't need PCM... If you turn your transmitter off, or taxi too far down the runway
the ECU kills the Engine.. I have done both many times and it works every time... Other ECU may do the same thing..

I greatly perfer PPM with all the Glitches.

Eddie Weeks
http://www.variablepitchhobbies.com/

RE: Really Stupid Question
 

Eddie

I have to agree with you, being an AMT user myself as well as a Multiplex PPM one. The AMT system (and I'm happy to acknowledge any other brand with the same features) is also set to a 200ms rotation delay - that is the time the ECU will allow the Rx to return to the same channel - before it will shut down the turbine. Most Rx's are doing a full rotation in about 50ms and therefore the AMT ECU system will easily fit into any failsafe delay requirement. With the Multiplex IPD PPM Rx I can only comment having used the 12 ch - normally I only use straight PPM - and having had Mpx do an update on the rotation speed as I was getting enigne cuts from my AMT ECU's due to it being too slow. After this update the 12ch IPD Rx seems fine. However, I'm about to use a Micro 7 IPD and would like to hear comment on it's performance. Overall these Mpx Rx's are great and work very well with all other radio transmitters. BTW, some of them even have a dual battery redundancy system built in too.

However, given the choice I will always choose PPM over PCM as the only time I've had a radio system induced crash it was with PCM. So after more than 500 turbine flights since then, I will not risk it again.

Springbok Flyer