rcjets_63

My Feedback: (4)

Radio System and Gyro Installations – Continued

The cables to the wing servos were routed from the Cortex and along the sides of the fuselage at the wing roots. A small slot was cut in the wing spar forward former to allow the cables to be routed around the spar receiver tubes, and rearwards through the existing cutouts in the wing spar aft former. The servo cables exit the fuselage via a ½” diameter hole was cut 3-1/8” aft of the aft edge of the wing tube.

By shining a light into the elevator servo cutout, I could see the structure of the wing root rib which has triangular shaped lightening holes. I ground a hole through the fiberglass over the root rib for the servo cables to exit the wing. A small slot was cut though the rib between the aileron and elevator servo cutouts to enable the aileron servo cable to be routed forward of the aft spar. A servo cable extension was added to the aileron servos.
The connections to the CB200 were as follows:
In the case of the Gripen, all ports were being used as follows:

(left side of CB200)
SW – switch
8 - Brakes/Tank Drop
7 - Airbrakes
6 - Gear doors
5 - Nosewheel steering
4 - Left canard
3 - Retracts
2 - Right elevator
1 - Rudder

(right side of CB200)
Rx 1 – connection to receiver 1
Rx 2 – connection to receiver 2
Ext1 – EX4 expander
15 (or Ext 2) - Lights
14 (or Ext 3) - Right canard
13 – Throttle
12 - Cortex gyro gain
11- Left aileron
10 – Right aileron
9 – Left elevator

This layout simplified the routing as servo wires coming from the left, right, front, and rear portions of the model are installed in ports located on the left, right, front, and rear ports, respectively, of the CB200. This reduces cross-overs, and makes the installation neater. The port assignments for the servos are a bit funky for the ailerons, elevator, and rudder, but it ensures that there is a 3-wire lead going from the Cortex to each side of the CB200. The single wire leads going to neighboring ports are tie-wrapped (for support) to the 3-wire leads.

Here are some pics of the completed installation:


Regards,

Jim

rcjets_63

My Feedback: (4)

Receiver Installation

Two R3 receivers were installed in the model as follows:

Rx 1 – installed on the canard former with the antenna routed behind the cockpit (high point on the model) with one antenna oriented left/right and the other antenna oriented up/down. The selection of location and orientation is intended to provide primary reception when the model is flying towards me (such as when making the turn upwind). From a safety perspective, this is a critical orientation as loss of signal at this point could be particularly bad. By placing the antennas high and providing the left/right & up/down, the collisions between the horizontally oriented DC-16 transmitted RF pattern and the receiver antennas are maximized regardless of roll angle of the jet.

Rx 2 – installed on the right side of the model with one antenna oriented fore/aft on the right side to augment the up/down and left/right antenna orientations of Rx 1. Between the up/down and fore/aft antennas, there should be good reception of signal on the back side of the circuit when the side of the aircraft is presented. The second antenna is oriented left/right and is installed on the bottom of the fuselage to provide greater antenna diversity flying directly towards or away from the transmitter.

Telemetry Sensor Installation:

The CB200 default setup has one dedicated Ext port for external sensors and 15 ports for servos though ports 12-14, can be changed to Ext ports via the firmware if they are not being used for servos. In the case of the Gripen, all ports are being used so an EX4 telemetry expander was required.

The installed telemetry sensors include:
-Xicoy ECU sensor (installed in mid-fuselage) providing engine, fuel, and ECU battery info
- MVario barometric altitude sensor (installed in mid-fuselage)
- MBar air system pressure sensor (installed on forward component board)
- MSpeed pitot airspeed system (installed in nose as connected to expander port on MBar)
- MUI-30 initially connected to fuel pump but will be moved to hydraulic pack (see below)

I’ve got the Xicoy ECU sensor installed on my RePhantom but I haven’t had much luck getting the fuel gauge correctly calibrated. The fuel capacity setup is simple; you simply go into the menu and set the size of the tank. You then fly and, upon landing, adjust a value in the sensor such that the displayed value of fuel remaining matches the actual amount of fuel remaining. It should take a few flights to dial that in. I must be doing something wrong, because the first flight (using the default value of 400) showed that my tank was empty when I landed when I actually had plenty of fuel left. I changed the value to 300 and the sensor still said empty when I had plenty of go-juice left. I guess I’ll try 200 the next time.

Since I haven’t had much luck (yet) with the Xicoy sensor, I will use the Jeti MUI-30 (spliced into the fuel pump line) which I have used successfully as a fuel gauge and flameout detector with JetCat engines previously installed in my Rafale and Reaction. Once I get the Xicoy sensor sorted out, I’ll move the MUI-30 over to monitor the hydraulic pump battery.

Here are some pics of the installed receivers and sensors:


Regards,

Jim

rcjets_63

My Feedback: (4)

Nose Gear Forward Door

The front of the kit door includes the raised panel for the taxi light window. The panel is sightly incorrect in size, shape, and location and was sanded off and the scale hole ground/filed through. A scale panel will be made from clear lexan, the circle masked, and the panel painted. Therecessed flange on the bottom edge of the door is also missing and needs to be added.


Here are some pics of the finished nose gear door assembly and the slots for the brackets attached to the nose strut.. The brackets for the linkage were made from .030 thick G-10 and the linkages were built using Dubro turnbuckles and brass tubing.


Regards,

Jim

rcjets_63

My Feedback: (4)

Windscreen and Canopy Attachment

While the stock kit has the windscreen and canopy glued to the exterior of the model, I figured this would compromise the final look of the model. Thus I cut off the bow frame and molded a new one with a mating canopy frame such that the canopy and windscreen are installed from the inside. This was covered in earlier posts (~ Dec 2014).

The canopy and windscreen were installed using the RC54 canopy glue and magnet method.


Regards,

Jim

rcjets_63

My Feedback: (4)

Taxi Testing

Finally, the jet had progressed to the point where it could move under it's own power. I like to do taxi tests on the street in front of the house rather than at the the flying field. My neighbors don't mind and often come out to watch. For me, it was a thrill to drive the jet around after the months/years of building effort. The maiden flight will be next weekend which gives me a week or so to set up all the throws, alarms, modes, etc and double check everything.

The pneumatic wheel brakes worked just fine as expected. The steering was about right with high/low rates of 60/75% with 30% expo.
http://youtu.be/oAMIom8PVB8 Regards,

Jim

marc s

All the best for the maiden Jim, amazing diary of the work that goes into this competition.......

marcs

RCISFUN

My Feedback: (44)

Jim, awesome job, you have raised the bar on build threads and documenting!
I wish I had that kind of time!

Ron S

My Feedback: (2)

Jim - first flight next weekend in Tucson??

rcjets_63

My Feedback: (4)

Marc & Rich,

Thanks, the plane and the thread have been a lot of work but I have enjoyed both. Roy Maynard will be starting the build of his AW Gripen soon and I thought it would be helpful to put a bunch of info in one place where he could find and make use of it easily. Perhaps this thread might encourage others to build this plane too. AW Gripens seem pretty rare and there are only nine of them (shown below) that I'm aware of having flown and none of them are in the US. That's not a lot for a kit that has been around since 2006. Of course, now that I know the work that goes into one (even building it stock) I can understand this. My hat is off to all the builders and pilots below, especially Tom Storvik who built two.

The build (and build thread) certainly isn't done. Off the top of my head, the following items remain: finish (sand, fill, paint, dry transfers, weathering), taxi & landing light, molding scale pylons (wingtip #1, outboard #2, inboard #3, right inlet #4, belly #5), working MFD displays in cockpit, scale details (vents, louvers, openings, aileron hinge fairings, landing gear details, etc). There is still LOTS OF WORK to do before Top Gun and even more before the Jet World Masters.

Ron, unfortunately I didn't have the plane ready to flight test at Tucson. As it turns out, a mandatory course was scheduled for yesterday and today at work so I couldn't go to Tucson anyway. The maiden flight will be off the lakebed in Kingman, AZ next weekend.

Thomas Gleistner (prototype) - Germany

Janne Seppanen - Finland

Tom Storvik (2) - Norway

Radek Suk - Czech Republic

Martin Forster - Switzerland

Boris Satovski - Russia

Ali Machinchy (pilot), builder not known - England

Sven Schleyer

Regards,

Jim

Ron S

My Feedback: (2)

Jim, you do know that Tucson is next weekend, not this weekend? Either way, good luck with first flights - this will be a cool project to see fly!

sysiek

My Feedback: (176)

The jet looks grate with all the sharp lights Jim ,grate progress and the hardest work finish.

rcjets_63

My Feedback: (4)

Actually, I screwed that up. I thought Tucson was this weekend instead of next weekend. I even called Dan Avilla while I was stuck in class to ask about how the event was going. He called me back tonight and straightened me out.

So this is a bit of good news and bad news. The good news is that I don't have to wake up early tomorrow morning to get down to Tucson. The bad news is that I have already made arrangements to go up to the lake bed next Fri/Saturday with a buddy (who is supplying the vehicle - the Gripen doesn't fit in mine) to maiden the thing. It is against the rules to maiden it during an event so doing the maiden at Tucson is out of the question. I can't put it off for another week as I need all the practice flights I can get on it as possible before Top Gun. I haven't missed a Tucson Jets since moving to AZ in '08 but I fear that I might not make this one

rcjets_63

My Feedback: (4)

Telemetry Alarms

I've got quite the suite of sensors (MVario2, MSpeed, MBar, MUI-30, and Xicoy) in the Gripen which are sending back to the transmitter 31 different data items which are automatically recorded once per second into a log file which is stored in the transmitter. You can go back an look at the log file at any time.

Having this data can be very handy for several reasons including:
- looking at any trends over time. For instance, a recent increase in max pump voltage can tell you that your filter is getting plugged or your pump is wearing out
- looking at data from the last flight. I had a guy jump all over me telling me that I exceeded the 400 ft altitude limit they have at their field. I pulled up the log file and showed him that my max altitude during that flight was 379.6 feet. That shut him up. (I knew I hadn't blown the limit because, when I fly at that field, I put in warnings for 350, 380, and 400 feet, and I didn't get the 380 or the 400 warning.)

The alarms I have initially put in the Gripen are:

Receiver Low Voltage Alarms
Receiver 1 voltage < 5.9V - plays wav file "Alarm - Receiver 1 Voltage"
Receiver 2 voltage < 5.9V - plays wav file "Alarm - Receiver 2 Voltage"
Note: The voltage at the receiver is expected to be slightly lower than at the CB due to voltage drop over the EXT cable

Receiver Battery Alarms
CB Voltage 1 < 6.3V - plays wav file "Alarm - Battery 1 Voltage"
CB Voltage 2 < 6.3V - plays wav file "Alarm - Battery 2 Voltage"
I'm using A123's so I set the value at 6.3V. With LiPo's or LiIon's I would have used 7.2

ECU Battery Alarm
Xicoy ECU Bat < 9.5V - plays wav file "Alarm ECU Battery Voltage"
The Kingtech 210 used a 3S LiFe battery. The alarm is set below 9.9V (nominal) as the high current to the kero plug during startup can pull the pack to 9.6V

MUI-30 Alarms
I have the MUI-30 currently spliced into the fuel pump cable to measure the mah used by the fuel pump (which is surprisingly linear with the quantity of fuel pumped). Once I get the Xicoy fuel gauge working to my satisfaction, I will remove the MUI-30 from the plane and use the Xicoy fuel and fuel pump voltage. In the mean time:
MUI-30 Amp < 0.1A - plays wav file "Flameout Flameout Flameout" Alarm is armed by moving switch to hi throttle trim.
MUI-30 Capacity > 400mah - plays wav file "Warning Bingo Fuel, Bingo Fuel"
MUI-30 triggers to automatically reset the capacity value when pump voltage passes from 0 to 0.1A
MUI-30 Voltage < 7.2V plays wav file "Warning HPU Battery Voltage".

MBar Alarms
Pressure < 551.6KPa (80psi) plays wav file "Alarm Low Air Pressure". Alarm is armed by moving switch to hi throttle trim. This is akin to a failsafe, and I could have programmed the radio to drop the gear, but instead I just use the warning and I will lower the gear myself.
Pressure < 689.5KPa (100psi) plays the wav file "Warning Low Air Pressure - Do not take off". Alarm is armed by moving flight mode switch to Take Off. This warns me if I forget to refill the air system pressure (nominal 115psi)

MSpeed Alarms
Speed > 320 kmh (200mph) plays wav file "Easy Thunder! 200mph speed limit exceeded". I should never get even close while flying the plane in a scale style.
Speed < 70kmh (44mph) plays wav file "Stall warning Stall warning" I will fine tune the value based on the flight tests

MVario2 Alarms
Rel altitude < 3m (10 ft) plays wav file "Terrain, terrain, pull up, pull up." Alarm is armed by raising landing gear. The Scalemasters altitude range for a flypast is 10-30 ft.
Temp < 15C (59F) plays wav file "It's too damn cold to fly; this isn't Canada, or Pennsylvania". Alarm is always armed!

In addition, there are the standard system level warnings & alarms for antenna strength

rcjets_63

My Feedback: (4)

Landing Gear Machining Error

I had noticed a while back that there seemed to be a problem with the main landing gear in that the right strut compressed more than the left strut. As the heavier components (engine, batteries, fuel) were installed in the plane, the difference became much more obvious. Just sitting on the ground with the wings off, the right strut compresses about 13/16" more than the left. I called Roy Maynard and asked him to check the gear of his unbuilt model and it also seems to have the same issue. Hmmm. Something funky is going on.

The easiest explanation seemed to be the springs. The Gripen struts each have two coil springs. The lower spring is a light-duty and essentially fully compresses with the weight of the model. The purpose of this spring is to help keep the oleo strut fully extended as the gear goes up so that the tire clears the door. The upper spring is a heavy-duty spring that compresses slightly under the weight of the model but essentially is intended to absorb landing loads. There is an aluminum adapter between them. Here's a pic:


I suspected that the issue was the springs themselves because there were minor length differences between the light spring in the left strut and the light spring in the right strut. The same was true of the heavy springs. However, the differences in length weren't enough to explain the 13/16" overall difference in strut compression. I suspected that one of the springs may have been poor quality an had a much lower spring constant (force to compress the spring a given amount) so I got out the force gauge and found that they were all pretty close. So I looked harder and found the problem.....

Here are photos of the right lower strut. Notice how the steel tube has been drilled out (ID ~14.05mm x 18.25mm deep). The major diameter of the aluminum adaptor is 13.98mm and fits nicely down into the lower strut (I didn't install the light lower spring for the photo) and has bottomed out. The chamfered edge of the adaptor mates with the angled end of the drilled bore.


Here is the left strut. It hasn't been drilled out and the aluminum adaptor won't fit down into the lower strut. This limits the amount that the light spring can compress and, to make matters worse, puts a pre-load on the heavy spring so it won't compress as easily during landing and will transmit greater landing loads to the strut and airframe. :-(


So, the left strut needs to be drilled out. Rather than buying a 14mm drill and trying to do it myself (without the right clamps to hold the strut), I'll bring the strut to a local machine shop on Monday to have it done professionally.

This is really a HUGE quality miss on the part of Airworld and their landing gear supplier. One would expect better than this in an $8000 kit.

I'm also not too impressed with Airworld customer service these days. I've sent two sets of emails to two people at Airworld asking for the control throws and neutral positions of the elevator & ailerons. In a week I have received no response.

Regards,

Jim

NRTM

Hi Jim.

What airbase is it you going to visit? If it is F7 and if you got time we can meet up so you can se our Gripen live?
F7 is only 30km from the field that we have made most of the tesflights.

www.jetsweden.se
www.scaledetails.se

Regards
Niclas Robertsson

rcjets_63

My Feedback: (4)

Niclas,

I sent you an email via scaledetails.se

Regards,

Jim

RCISFUN

My Feedback: (44)

I almost spit out my coffee when I went back and read this...too funny!

rcjets_63

My Feedback: (4)

Glad you enjoyed that Rich. Actually I need to change the temperature alarm to 11C or 51F. There is a rule here (well, guideline really) that when the temperature in degrees F is less than your age in years, you stay home. It really is a good rule.

In other Gripen news, I managed to get the landing gear strut machined at a local machine shop. They didn't get the counterbore quite straight (workpiece slipped in the clamp) but it appears to be good enough.

Control Arms Setup

I am using SWB aluminum arms installed on the aileron and elevator servos as they come with a 1/16" thru holes (with plastic bushing) suitable for use with a clevis which is needed for the pushrods to fit (easily) under the fairings. The pushrods are made from 4-40 all thread with a carbon fibre tube Hysol'd around them. The pushrods are fitted with a Sullivan Gold-N-Clevis at the control horn and the plastic clevis (to prevent the pushrod from rotating) at the control arm. The great thing about these arms is that they use a the regualr servo screw and additional have a 2-56 SHCS and safety nut which tightens the arm onto servo spline. It is alot easier to remove the SWB arm than a Hanger 9 arm aluminum arm. BTW, for anybody concerned about the strength of the plasic clevises, I did a pull force test and the G-10 control horn breaks before the clevis (and the G-10 arm is 1.5 times as strong as the stall load of the 8711 servo). .


I spend a lot of time trying to get the mechanical setup done correctly (and the same on each wing). I found that it is alot easier to get the sub-trim/neutral position set consistantly by using CA to spot glue a balsa strip to the side of the control arm. A carpenter's level placed on the wing gives a good reference for alignment. After the sub-trim is set, just pop off the balsa strip.


Because I am doing internal linkages, the distance from the control horn clevis hole to the hinge line is only about 5/8" for the elevators and 3/4" for the ailerons. As such, to get the "recommended control throws", I needed to reduce the servo endpoints to about +/-30% on the Jeti (+/- 38% on JR or Futaba). This is less than I am comfortable with (lose too much resolution) so I modified the 3/4" SWB arms by drilling 1/16" clevis holes at the 1/2" positon. The slots in the lower wingskin had to be extended to clear the rods.

Regards,

Jim

rcjets_63

My Feedback: (4)

Airworld Recommended Control Throws:

Radek Suk (Czech Republic) sent me a copy of the Airworld recommended control throws which I have translated from German as follows:

Canards

The canards are mixed to the elevator for take off only. The maximum deflection at full up elevator is 40mm up measured at the leading edge of the canards. The mixer should be disabled after take-off, so that the canards iare in the neutral positon for normal flight and landing.

Ailerons

For take-off, the ailerons are mixed to elevator to give 25mm up & 10mm down. For normal flight, the ailerons are not mixed to elevator and have movement of 25mm up & 30mm down.

Elevators

Elevators moves 40mm up & 30mm down

Rudder

Rudder movement is 30mm to the right and left

Regards,

Jim

rcjets_63

My Feedback: (4)

My Initial Control Throw Set-up

We've likely all seen cases where the manufacturer recommended control throws leave a bit to be desired so I always try to get a second (or third) opinion from someone who has flown the plane. Comparing the Airworld setup to Janne Seppanen's (as posted in the AW Gripen thread) and Martin Forster's there are some similarities and differences.

Elevators: 40mm up, 30mm down measured at the fuselage. Everybody agrees on this so that's what I'll use (with 30% expo since that worked well on my SM Gripen). The AW photos (above) suggest that the neutral point is with the elevators even with the fuselage. However, here is a pic from Martin Forster that shows his elevators are trimmed a bit down. I will set up the neutral even with the fuselage and will be prepared to add some down trim, if required, during the maiden


Ailerons: Janne said about 20mm up/down measured at inboard side but there may be some differential. Airworld recommends 25mm up & 30 down at the outboard side. This is a big difference. I also find it strange that they recommend more down movement than up movement as more up movement is typical to counteract adverse yaw. I will go with 25mm up/down measured at the outboard side on high rates and 25 mm up/down on the inboard side at low rates and have 30% expo. For take off mode, the ailerons are mixed with elevators and travel up 25mm and 10mm down (measured at the outboard side (with is a bit less angular movement than the elevators).

Rudder: 30mm on low rate. 40mm on high rate. I'd like a bit more deflection (than the AW recommendation) for the gyro to be able to counteract the Dutch roll tendancy that delta wing planform aircraft typically exhibit.

Canards: Here are some pics from Martin Forster showing the control surface deflections at the moment the plane is rotating for takeoff and just before touch down when landing.

In the landing pic above, the canards are up about 10-15mm. I had a lot of luck using a 9mm up offset my 1/7 scale SM Gripen canards for landing mode (elevator/canard mixing off) as it helped establish a positive AOA. For a 1/5 scale, the equivalent measurement is a 13mm offset. Everybody seems to agree to turn the canard/elevator mix off for landing.

In the rotation pic above, the canards appear to be at about 20mm up and the elevators are at full up (40 mm). For take off mode, the canards are mixed with elevators. I've programmed an offset for 20mm up canard when the elevators are neutral. This should help in rotation to smoothly raise the nose without a lot of need for elevator input which leads to the famous Gripen leap. With full up elevator, canard leading edge root is 45mm up.

The canards are also mixed to brakes (activated by logical switch of gear down, landing mode selected, and brake lever past 1/2 travel) to deflect downwards for aerodynamic braking.

The thrust line on the plane is quite high and Martin, Thomas, and Janne have all suggested not to use full power on the take off roll (suggested 70%). Full power tends to push the nose down (compressing the nose gear and preventing rotation). Janne suggested increasing the stiffness of the nose gear spring. Using the stock setup, the nose gear compresses about 1/2 way (10+ mm) from the weight of the plane just sitting on the ground. He changed the spring such that the nose gear doesn't compress at all from the weight of the nose. He also substituted lighter weight springs on the mains to give a more positive AOA for takeoff.

I think (hope/guess) that my canard setup will help reduce the leaping on takeoff, but I also decided to stiffen up the nose gear spring so it doesn't compress under the weight of the nose. The nose strut compresses about 1/2 way with 10 lbs of down force on the strut. I stiffened the spring by installing a 1/2" diameter x 1" long wooden dowel in the nose strut above the spring. Now the nose strut starts to compress with 10 lbs of down force.

Regards,

Jim

rcjets_63

My Feedback: (4)

Landing Gear & Brake Lines

I had the landing gear strut corrected at a local machine shop and now the left & right struts compress the same amount and the plane sits level. :-) The struts and drag links have lots of joints held together with slotted pins and e-clips. This is probably OK for most of the joints, except the mid-joint on the scissor link. Unless the pin is exactly the right length, there will be some toe-in/toe-out play. As such, I changed this joint to a 3mm SHCS and safety nut.


The nipple for the brake line is at the front of the axle block and points upwards, as opposed to the full scale which has the brake hose connection near the bottom aft quadrant and facing rearwards. This doesn't help with the scale brake line routing, but at least we can route the line up the back of the strut, per the full scale. Tidy-strips were CA'd to the back of the strut to hold the brake line in place. A quick disconnect was installed on each brake line and mounted to the forward spar former to allow the gear. If the QD is small enough, it can fit thrugh the gap between the upper strut and the rear retraction bracket for easy removal of the low strut without having to cut the air line.


In other news, the piaint and weathering supplies arrived yesterday from Tailor Made Decals. Many thanks to Ralle at Tailor-Made for his support of Jet Team USA.


Regards,,

Jim

jettom

Hi
The most importen thing when take off is not too have full power on the turbin.


Tom Storvik

rcjets_63

My Feedback: (4)

Tom, thanks for the advice. I'll remember!

Maiden Flight Day

Well it is finally here after so many months, actually years, of work. I bought this jet on 4/16/11 and have worked on it off/on for four years. The serious work started in earnest back in October 2014 and I've pretty much worked on it almost every single day for 4 hours per week day and 12 hours per day on the weekend. Adding it up, I've got over a thousand hours into this build and it's not done yet. There is still the finishing prep, painting, weathering, and scale details.

Here are some of my favorite pics from the experience, though.


Wish me luck! I'll post news & pics as soon as possible.

Regards,

Jim

marc s

Good luck!

marc

NRTM

Good luck from Sweden!

www.jetsweden.se
www.scaledetails.se

regards
Niclas Robertsson