RE: A beginners guide to jets, revised
 

Al,

Gee, I thought that was clear as mud, but then again it always sounds perfectly clear to the guy who is writing it! Let me see if I can muck it up a bit more. Seriously, let me take one more shot at this.

Groundspeed is airspeed plus or minus the wind. Airspeed is the actual speed of the relative wind over the airplane. 40kts airspeed with a 20kt headwind equals a 20kt groundspeed. 40kts airspeed with a 20kt tailwind equals a 60kt groundspeed. In both cases, your airspeed is still 40kts.

It's all very easy to understand as long as you are dealing with a steady state wind. When the wind gets gusty or rapidly changes direction, the dynamics change. In that case, indicated airspeed can fluctuate greatly with no change in power.

The first issue deals with aircraft momentum or lack thereof. It you have 40kts of airspeed in 20kts of steady state headwind and the headwind suddenly stops, what happens? Is your airspeed still 40kts? No! Believe it or not it's 20kts! This confusing little issue has been the cause of a number of windshear crashes before the phenomenon was understood. Let's say an airliner is on final at 130kts and flies into a downburst. These typically hit the ground and fan out, so if you fly into one you get hit with an instantaneous headwind, followed by a horrific downdraft, and then a huge tailwind. So let's say an airliner is initially hit with an instantaneous headwind of 50kts. The pilot will see an instantaneous increase of 50kts on his airspeed indicator. He pulls back the power to maintain approach speed. Next, he hits the core of the downburst then rapidly enters a 50kt tailwind, which results in an instantaneous decrease in indicated airspeed of 50kts. So there's the airliner, thrust pulled way back to maintain 130kts, while his groundspeed is actually 80 knots and he's getting pushed into the ground by a downdraft. Next, he gets hit with an instantaneous decrease in indicated airspeed of 50kts. In that scenario there is no chance of recovery. A crash is inevitable. That's why airliners use wind additives on their approach speed, so the airplane will have enough momentum to deal with the airspeed fluctuations. Nowadays, of course, thunderstorms and downbursts are avoided, and it is a typical policy to abort the approach if airspeed fluctuates by more than plus or minus 15kts below 1,000 feet.


The second problem deals specifically with model airplanes. How do we judge airspeed? By eye. By observing how fast the airplane is moving. But relative to what? The ground! We fly by groundspeed because that is all we have to work with. So we fly by "perceived" airspeed. Here is were the problem lies, and as Erik has said, it has claimed many a model airplane! Let's say our model stalls at 30kts and we are flying into a 20kt headwind. A normal approach speed would be stall speed times 1.3, or about 39kts. We fly our model at what LOOKS LIKE 39kts to us. Now lets say we suddenly lose that 20kt headwind, our airspeed will instantaneously drop to 19kts! So based on the concept of "perceived airspeed" we kind of have to make a little adjustment in our heads. If we adjust our throttle setting to maintain a constants perceived airspeed in gusty situations, we are actually adjusting our actual airspeed without knowing it! This problem manifests itself in the worse way under three situations; the turn to downwind, the turn to final, and final approach under gusty wind conditions.

Granted, this is all a bit much for an RC flyer to keep in his head. The bottom line is to remember we fly model airplanes based on perceived airspeed, not actual indicated airspeed. The actual airspeed of the airplane may be faster or slower than it appears. Be cautious going from headwinds to tailwinds. Keep in mind the airplane cannot make instantaneous changes in actual airspeed to account for sudden fluctuations in wind.

RE: A beginners guide to jets, revised
 

Many modelers judge the airspeed of their model by guessing...throttle setting is only one piece of the "airspeed" equation. Configuration and angle of attack complete the picture.

IMHO, the best judge of airspeed is by knowing the aircraft angle of attack for a given throttle setting and configuration at stall speed, then keeping the angle of attack less than that to remain above stall speed. The only way an RC turbine pilot can discover this is to run the aircraft through a series of stalls at altitude. Overly mushy controls are also a good indication of impending stall for many jets.

Knowingly flying at a higher airspeed to maintain a familiar ground track will keep an aircraft safe when experiencing gusting headwinds. For steady state headwinds it is still a good practice to fly a little faster airspeed and make the approach and landing look familiar in terms of grounds speed and track. A short, steep approach with a lot of headwind can result in disorientation when it comes to the flare and touchdown. The increased airspeed on a calm day would take up a lot of runway, but with a stiff headwind the landing can look fairly normal with an average roll out distance. The higher throttle setting will be convenient if a go-around is necessary, since there will be little turbine lag.

Watching angle of attack of the aircraft on the "downwind" part of the pattern will help avoid stalling, specifically with flaps at approach and gear down. The groundspeed will be higher than what looks "normal" due to the stiff tailwind, but trust the angle of attack for this configuration (memorized from a calm day) to judge the airspeed. Resist the urge to pull the power back further than usual on downwind.

With crosswinds in the face, making a pattern slightly wider than normal will allow spacing to keep the aircraft on speed (angle of attack) and avoid the dreaded "base leg stall" when banking up for the final turn. No better way to make the flightline Safety Officer nervous than an overshooting final with an RC turbine headed toward the pit area while it is getting slow and on the verge of tip stalling. Less bank and under complete control to touchdown will inspire your local Safety Officer to ask you for landing advice. ;)

RE: A beginners guide to jets, revised
 

Updated RC Turbine Checklist for your consideration. Feel free to use it to make your own checklist, take it as is, or disregard. I'm still interested to see if anyone else has a checklist they use as a training aid for new turbine pilots. As a volunteer RC instructor pilot this checklist will help me give students a repeatable standard born from recommendations by those in this hobby we look up to.

Just like with full scale jets, a checklist is a good way to make sure everything important is briefed to the crew and completed on time. If we fly at an AMA approved flying site as part of an AMA chartered club we are required to use a spotter while flying RC turbines...so the two of us are a crew at that point.

Our increasingly critical political environment, in general and in our clubs, will require more vigilence. How our club members perceive us as jet pilots is almost as important as how safe we really are.

Your thoughts? What do you use as "memory joggers" to safely operate your turbine models?

Jet stick planes are the next step in club proficiency...practicing a flight before performing it will help people visualize maneuvers and remove ambiguity. I got these from Callie's Graphics. She prints vinyl that matches your jet exactly, if you want. She can also do some generic schemes (www.callie-graphics.com).

***Updated RC Turbine Checklist*** to incorporate Sparhawk's recommendation...RX off first, then TX. If your system requires something different, modify the checklist for your needs. Thanks Sparhawk!

RE: A beginners guide to jets, revised
 

Albert,
Really great thread developing here, especially for the noobie jet pilots. I printed off a copy of your checklist to show at my local R/C club meeting tonight. This club has a current ban on turbines and I'm trying todemonstrate oursafety awareness to get the ban lifted.
I also recommend having your RCTurbine Aircraft Checklist posted on the JPOwebsite (www. jetpilots.org) as a document. Just contact Keith S., JPOPrez, to get this accomplished.
Again, many thanks on compiling this checklist and to all that contributed to this thread. This is what the RCJets forum should be about.

Art ARRO

RE: A beginners guide to jets, revised
 

I too use a checklist, it is printed and laminated and sits on the ground in front of me as I prep a jet for flight. I use it every time, start at item 1 and work my way through. Things like fuel valve to closed before fuelling, all aerials in place, batteries load tested, overflow tank attached, fuel filler bung replaced before start up, all air systems pumped up, etc etc. Then I follow the BMFA suggested process for the Tx of SMMART - Switch Tx on, Meter (battery meter ok), Model (correct model memory selected), Aerial (not such an issue now with 2.4Ghz but a check that the LED's on my Weatronic and Multiplex modules are showing correct blink codes), Rates (rates switches etc to correct position) and finally Trims not such an issue now with digi trims but my fav old tx has mechanical trims so it's still valid. Finally to the model I count 4 items - Battery 1 on, battery 2 on, turbine battery connected, manual fuel valve open.
By following the routine of printed lists and memory pnemonics like SMMART I am always confident that everything is ready.

RE: A beginners guide to jets, revised
 

Art ARRO, precisely the reason the jet guys need to step up and lead...being safer and more disciplined, so no one needs to question the preparedness of the turbine pilot...nor the proficiency.

HarryC, I like your technique. Using something that is easy to remember is also a great way to guarantee success. Maybe we can come up with pneumonics for each of the checklists if we work together. Before start, Starting, Before Taxi and Takeoff...not sure if that is doable, but it could improve my checklist by making it easier to memorize. Mine is mainly for those first few times to the field after a winter break, or for getting a club to start thinking more seriously about turbine safety. I'd like to pay more than just lip-service to safety and proficiency.

Gents, I'll send it to Mr. Seivers to see if he's interested in posting it in the Knowledge Wall section of the JPO website. It would be better if there were several choices, and people could even make their own from the samples there.

Who out there is a current turbine instructor? What tools do you use to teach...or do we do any teaching at the advanced pilot training level? I'm batting around the idea of putting on a full day "Turbine Training Clinic" for free out in Northern California in the Spring of 2014. Maybe have a small landing fee that covers lunch.

This will be a purpose driven get-together for learning at all levels...from just getting new people airborne, to getting people through their turbine waiver check and working with some of the more advanced turbine pilots in the area to demonstrate and teach good techniques for high energy flying, good airspeed management and overall proficiency flying high performance turbine aircraft. I'm a CD, but people with specific strengths to teach different parts of the Clinic and two or three "roaming helpers" could make this a hit...even if there were only ten turbine pilots that show up.

Ideas?

RE: A beginners guide to jets, revised
 

After HarryC posted his info including the BMFA resource, I went to the site to see how the UK certifies turbine pilots. In the past I've also visited the MAAC site to see how Canada does it.

Check out the Basic "B" class training syllabus below, called the "Radio Control Achievement Scheme." It is a little more thorough than your average club's training program here in the states. The picture is of the first page, the link to the full PDF is here:
http://www.bmfa.org/achievement/2004...ide-Issue1.pdf

How many non-UK turbine pilots could complete the Gas Turbine Achievement Test in the chart below? It is found in a pretty comprehensive document here:
http://www.bmfa.org/achievement/files/2013/C(GT)-2013.pdf

For more in-depth reading, in preparation for a new flying season and to gain more perspective as a safe pilot, check out the BMFA "Code of Practice for Operation of Gas Turbine Model Aircraft:"
http://www.bmfa.org/publications/fil...ssue%202CB.pdf

My goal, to push my flying to a level defined internationally, is to be able to fly the BFMA "C Certificate (Gas Turbine) Checklist" in one flight, with a smooth flow from one maneuver to the next. Anyone else up to the challenge?

How about a link to a video of this being done in less than 10 minutes?

RE: A beginners guide to jets, revised
 

Agreed, this is a good read.
Albert - The one thing in the check list I don't like is in the Post Flight section. You have the Transmitter power being shut off before the receiver power. I NEVER do it that way. Receiver power is shut off only while still in control by the transmitter. 2.4 or FM, this is the way it should always be done. Jets or prop planes makes no difference. I've seen gassers with failsafes not set properly go to full throttle... not fun. With jets if the turbine is off, it may save your flight surfaces in the accidental gear up glitch or other unforeseeable issue. Food for thought.

Dan

RE: A beginners guide to jets, revised
 

Sparhawk,
Good discussion point. Do you leave your transmitter on during the two minute turbine shutdown/cooling sequence?

Please explain how you operate your ECU and turbine shutdown sequence. I appreciate the feedback.

I've seen it done both ways at jet rallies and you bring up a good point. How does the rest of the RCU jet community do it?

AMA requires EVERY RC jet pilot to have their failsafe set to throttle down, trim down...how your control surfaces and gear are set up is up to the individual, though to use this technique the landing gear have to be "down" during failsafe operation.

Note: When a person first turns on most 2.4GHz systems, TX first, then RX, the system will still start with the failsafe condition, then go to the TX selected condition. Better have that gear down selected for the failsafe if you're turing on radio equipment after fueled and sitting in the pit area, with wheels on the ground. I can't imagine leaving my TX on that long, or picking up the jet while I turn on my TX, just in case my failsafe is set incorrectly.

Failsafe set up (throttle) it is part of the AMA basic turbine waiver check requirements and a person must demonstrate this knowledge.

My ECU power is always on when the RX is on...ECU battery is plugged in all day without a separate switch and unplugged at the end of the day. If there is enough of a demand for it, I'll go ahead and finish the "expanded edition" of the checklist which has each step, followed by a short paragraph explaining the step, logic behind it, notes, cautions and warnings that apply to it. The outline draft version includes articles in truncated form from advice I received from experienced RC turbine pilots, BVM, JPO and AMA documents on RC turbine jet landing, maintenance and proficiency training.

Yes, on my gassers, electrics, etc. I always turn off the RX first, then the TX and my failsafes are all set...most events with large models here in the U.S. have people demonstrate failsafe conditions before they are allowed to fly. For ALL RC models, TX on first, then RX...at least for the brands I use. I'm not sure if there is a brand out there that has a different requirement.

RE: A beginners guide to jets, revised
 

The latest JetCat ecu's power themselves off automatically and run cooldown even with rx off, just for info.

RE: A beginners guide to jets, revised
 

RC Turbine Checklist updated to reflect RX off first, then TX for safety, as recommended by Sparhawk. Thanks for the feedback!

click on the attachment for the full checklist, the pic below is only a clip to show the change...

RE: A beginners guide to jets, revised
 

No takers on the expanded edition of the checklist?

What do you all do for "Spring" proficiency flights to shake the dust off and get back to flying turbines? Any exercises you all do on the ground or in the air in the air to get proficient?

RE: A beginners guide to jets, revised
 

Albert,
I generally start myearly seasonR/Cflying with a HabuEDF or high performance propjet, like a Jett 50 powered F-20. In both cases I program a "throttle slow" to mimic the spoolup/down time of a typical turbine. I try to fly a set pattern of Figure 8s, loops, rolls and several landing approacheswhile simulating the use of flaps and retracts during these fam hops. Afterbuilding some confidence, I'll move to a simple turbine jet like a boomerang for more of the same. With several proficiency sessions logged, I'll graduate toa scale Skymaster Gripen which is a pretty high workload jet and sometimes difficult to see with itscamo paint scheme. This routine works for me although other jet pilots mayjump rightinto theirregular jets immediately. I personally have not found a flight sim to be helpful although others reply onone during the off season. To each his/or her own. Hope this helps.

Art ARRO

RE: A beginners guide to jets, revised
 

Sounds like a good progression...I'm also fond of the "thottle slow" function and use it to simulate turbine lag. Works pretty well I think. Go-around (aborted landing) practice!

RE: A beginners guide to jets, revised
 

I myself plan on starting my second year flying jets with some reaquaintance flights with landings on a long grass runway.

RE: A beginners guide to jets, revised
 

A long grass runway would be ideal...easy on tires too! Good luck with the new jets and the new season Joe!

RE: A beginners guide to jets, revised
 

Enough about proficiency and checklists...on to essential items that even the minimalist jet jockey will need to fill, pressurize and safely snuff on the flightline.

An avid RC pilot most likely has quite a few tools and support equipment already. To successfully get out the the flying field and be self sufficient, what "field equipment" is essential? What are "nice to haves?"

I've done a fair bit of research on my own by going to jet events and watching what "field equipment" worked well and was simple. I came up with these items as "necessary:"

Powered fuel pump/jug to fill those massive tanks with Jet-A/Kero/Diesel. Hand crank just didn't cut it.

Fire extinguisher. Most had CO2, some had Halon and other Halotron 1. Every flight box had a fire extinguisher that had a "clean agent" that could be ingested by the turbine, put out a fire, and not require cleaning or service.

Air pump. Electric retracts and brakes are catching on now, but even a year ago they were the exception. Still, most people seem to be using air systems, so they must be pressurized occasionally...before the first flight of the day and periodically to keep them functional. The capacity and required pressure of your system will determine what kind of compressor you will need. Large jets with big air tanks and higher pressure requirements will require more than your roadside assistance 12V compressor, while this tends to be a common solution among mid-to-small sized jet owners.

Fuel jug for mixing/storage. Since these turbines burn fuel at a rate unparalleled by any other RC aircraft, it is a really good idea to have a second 5 gallon jug in which to mix your fuel and store it, while refilling your primary pump container once in a while.

Lubes for brake O-rings, air system lube/conditioner. Keeps everything conditioned for a long, leak-free life.

Nice-to-haves:

Safety Wire Pliers and wire. Some method is required to keep things in place like air and fuel lines. There are several options, but safety wire is commonly used, very strong and has a much longer life expectancy than plastic zip ties.

Electric blower to help with turbine cool down. Extends starter motor life by giving it some help in turning the turbine and forces more cooling air into the intake, speeding up the cooling process.

Wagon. Pulling all the support gear out and getting it to the flightline can be done without a large garden wagon, but some people had them and could bring everything out at once, sometimes even with a jet on top of a built in rack.

Water filter funnel. Helps keep water out of the Kero/Diesel from the pump.

Water Trap for Air System. Keeping moisture out of the retract/brake air system prolongs the life of the system and keeps things from sticking.

I'm curious about your opinion/experience with what is must have equipment and what is "nice to have."

RE: A beginners guide to jets, revised
 

For those who are striving to convince their club officers or Board of Directors that turbine flying can be done safely, it might be a good idea to follow the recommendation of JPO and BVM with a good water fire fighting set up like the one below.

Water pump for fire fighting at flying fields:
http://www.forestry-suppliers.com/pr...efighting+Pump

"Drench" water additive for fire fire fighting:
http://www.forestry-suppliers.com/pr...itive&itemnum=

Biggest concern of many clubs is the fire resulting from a crash. Being able to wet the area surrounding the turbine model after a crash can significantly reduce the amount of fire damage, even in grass or dry areas. If a fire resulting from a battery or fuel cell cannot be put out with a fire extinguisher directly, wetting the area surrounding the burning wreckage will prevent it from spreading, especially in lower wind situations.

I'm not selling these, nor do I have stock in the company...just trying to increase awareness for a safe, fun flying season and maybe even see a few "new" turbine friendly clubs join the scene. [8D]