Firing up our Mach 0.75 Model Aircraft for the First Time!

[@TheMachInitiative]

**Response to FAQs included below** The aircraft works on the ground, the next step is doing a low-speed flight! We've also made a Mark II 3D-printed prototype addressing some of your comments and improving the TWR, to give the pilot some training on the day of the flight. This should be soon but is dependent on our pilot availability, test range availability and the weather all aligning. Also, sorry for referring to the test firing as a test flight in the audio, got a bit too excited on the day! *Edit: Thank you for all of your feedback and advice. To address some of the common themes:* 1. We’ve collaborated closely with experienced rc jet pilots throughout the design, the elevon linkages is something that slipped through the cracks and we assumed that having ball joints on both ends of the elevon linkages would under-constrain them causing us to incorrectly choose a servo side attachment that was unsuitable. We've already got some aluminium horns on the way, and we will be pairing these with a clevice. 2. We will be covering the elevon linkages with fairings, this was always the plan. 3. There will be different modes for the elevons as we increase the speed, this includes sensitivity modes on the transmitter and just controlling using the inboard elevons at higher speeds since these are smaller and are closer to the CG so have a smaller moment arm. 4. We will not be flying the aircraft ourselves, this will be handled by an experienced rc pilot with over a decade of experience flying fast jets. 5. The aircraft will be catapult launched, leaving the launcher at 50 mph. In order to achieve Mach 0.75 we use a high wing loading of 250 g/dm^2 to minimise drag, along with a 3:1 thrust to weight ratio. Our stall speed is high, but we have reduced this as much as possible by improving the lifting efficiency of our delta wing at low speed, high angle of attack, over common rc aircraft designs. This was the result of months of CFD and wind tunnel testing. 6. The inlet was optimised using CFD to minimise spillage drag at Mach 0.75 and ensure clean uniform flow to the compressor. This means it has a smaller than optimal opening at low-speeds which causes a 20% reduction in static thrust. Tom ran a large number of engine tests under varying cross flow conditions to ensure the engine doesn’t stall at low-speeds. The inlet is top mounted so that we can perform a belly landing. At the low angles of attack during take-off and high-speed flight, blanketing of the inlet from the fuselage is not an issue. This may cause some interference during the final landing approach where the aircraft reaches an 18 degree angle of attack just before touch down, but the engine is not needed for this phase of the flight. 7. We will evaluate the impact of fuel sloshing in the bags on the handling of the aircraft during the low-speed flight. 8. We will glue and seal the top panel down before flight. We want this to be one of the last things we do so that we can easily access wires if changes are required (although hatches enable us to access everything after its sealed, it just becomes a lot harder). As someone pointed out, we need to ensure this is completely sealed to prevent a build up of pressure inside the fuselage which could cause it to go bang. 9. To overcome the issue of fuel burn and flight time, we are developing an umbilical system that enables us to continue to fuel the aircraft up through startup right until launch, so that we leave the catapult with a full tank of fuel. 10. The aircraft features an FPV camera in its nose and will be flown with FPV assistance. We just need to post process the camera canopy to make it transparent!

[@waynesworldofsci-tech]

You need to make a Digital Combat Simulator version so the rest of us can fly her!

[@brucebaxter6923]

Awesome. Thanks for the faq. 1; what is your data logging/telemetry/failsafe system? Eg ardupilot. 2; have you considered fulll autonomous flight for a more controlled and stable flight? 3; are you measuring force(servo current) on your surfaces(unbalanced pull only not push pull or torque tube) Great work. Love to see this stuff

[@TheMachInitiative]

Thank you! 1. We’re running Ardupilot 2. We considered going automomous but we doubt we’ll be able to get permission from the CAA to do it 3. We’re not measuring servo current onboard, but measured control torques under varying conditions by placing strain gauges on the pushrods and putting the Kingfisher in the wind tunnel (will probs do a video about the wind tunnel testing)

[@brucebaxter6923]

@@TheMachInitiative That’s impressive. Strain gauges and wind tunnels. I was just thinking of running the current sensor on the 5v regulator. What country are you in? Here in Australia we can run all modes up to and including full autonomy as long as it’s line of sight and someone holds the tx. I do my testing with circle mode turned on about a quarter mile radius to give constant and almost level flight on the logs.

[@jayb2617]

@@TheMachInitiative I have seen first hand a 300mph jet and the hardest part is it will be out of range of your eyesight before it gets top top speed then you have to slow down, but good luck waiting for the maiden flight video

[@bdelapen]

I know that it has been said but it is worth reinforcing. At the speeds you are planning to fly linkage stoppers or EZ links are a no go, they will not be able to handle the flight loads. Also, your control throws are astronomical, at 200-300KPH (which is as fast as I have flown) we are already down to just a few mm for the control throws (2mm-5mm), you are planning to go twice to three times that speed so you will need even smaller throws. Your biggest enemy at those speeds will be control surface flutter: excess throws, weak linkages, unbalanced control surfaces, hinge line gaps of any kind will result in almost immediate catastrophic failure. Since you are in Europe look into how F5D pylon racer manufacturers set up their control surfaces and linkages, that will give you a good starting point.

[@frikkied2638]

Listen to this guy 👆

[@TheMachInitiative]

Thank you for your advice - we’ve learnt a stern lesson about the linkages and will correct this! Its worth noting we’ve worked closely with experienced rc pilots throughout the design, but unfortunately this is something that slipped through unnoticed - we incorrectly assumed that ball jointing both ends would under constrain the linkages and cause them to wiggle. The large throws are just for the test so we could easily see what the surfaces were doing. They will be dialled down with several transmitter modes for different speeds. These modes were sized using a MALTAB/ Simulink model of the aircraft which predicts control deflections along the flightpath. Also, we will just control using the inboard elevons at very high speeds for improved sensitivity. To mitigate the concerns about flutter we’re looking at how we can stiffen the elevons - will look into F5F pylon racer in detail, thanks for your support!

[@BigDuke6ixx]

​@@TheMachInitiative what is the predicted level or torque needed to move the surfaces at max speed? What altitude (QNH) are you going to do your speed runs? I'm really excited about this project.

[@frank-vq4mx]

@@TheMachInitiative I'm glad this was brought to your attention. The linkages are NOT robust enough for what you are trying to achieve. Also. On the servos. Are the control arms anodized aluminum or plastic?

[@TheMachInitiative]

The arms are currently plastic but we are waiting for aluminium ones to arrive

[@Nighthawk429]

Be careful with those long fuel bags. Changes in acceleration will force the fuel forward or backward, changing your CG. At the speed you'll be going, minor changes in CG will take you out of controlled flight faster than you or your gyro can react.

[@TheMachInitiative]

Thanks for pointing this out - we'll evaluate the sloshing in the low-speed flight first (as a more controlled environment facilitating greater reaction times) and will take it from there

[@ferdynandkiepski5026]

Also depending on your fuel system you might not be getting the fuel to the pump in certain positions. So some kind of baffles would be needed.

[@Murfster]

@@TheMachInitiative If it ends up being a problem you could design a fuel tank with internal baffles to control the speed of the "sloshing". It would obviously be more complicated than a bag, but I believe you could probably get away with something 3D printed.

[@TomFly]

In RC modelling we use them in hundreds of very fast jets. NO problems!!!

[@Radium_Productions]

@@TheMachInitiative the aircraft should be somewhat self stabilising if you manage to get the CoM a bit in front of CoL

[@FPVREVIEWS]

very exciting project. I'm working on a solar powered plane project, but this is interesting too. anytime you explained the frontiers of flight, it is a very good day! Even attempting to do so is great because you can learn lessons and share the knowledge. Great Job so far. Look forward to seeing flight tests and mach attempts in the future!

[@TheMachInitiative]

Thank you very much - just looked at your channel, your solar aircraft looks awesome, will watch the videos in detail later!

[@FPVREVIEWS]

@@TheMachInitiative Have you considered air launching your aircraft?

[@TheMachInitiative]

We would need a monster drone lift it in the air, and there is more risk with an air drop. We're going to catapult it.

[@TomFly]

You seem to be no RC Jet Pilots, if I see your Mount. Further on, you should reduce your servo throws down to a few millimetres. Use lots of EXPO to make it flyable. The most important part to be successful is CG !! If that is fine, and your rudders are doing fine, it might work. PLEASE: let it fly someone who has at least flown Jets of more than 500 km/h. If you are not familiar with those speeds, you will fail. AND: use a Gyro like CORTEX Pro in order to make it to fly smooth. CROSS MY FINGERS FOR YOU!!!

[@TheMachInitiative]

It will be flown by a professional RC jet pilot (not us)! The control deflections were much larger than in flight so that we could see the elevons easily during the test, they will be dialled down for the flight. We will also have multiple transmitter modes, and we will control using just the inboard elevons at high speed. The CG is something we've put a lot of thought into, we ran wind tunnel tests and foam model flights to find out the neutral point, and we've got an adjustable steel ballast in the nose to adjust the CG so its just ahead of the neutral point.

[@FernandoLopez-kp2jp]

What an outstanding achievement on such a complex project, really looking forward to see its first flight 👏 👏 👏

[@jackverna339]

Well done on the effort so far lads, even further well done listening and learning from those who have their own input and thoughts in the comments - it's not always asked for but can sometimes be valuable!!

[@gillwood]

Well done guys. Love the enthusiasm

[@lukebm5555]

Amazing project! Can’t wait for the flight tests. I’m also impressed with how you’ve responded to the feedback. Best of luck guys!

[@rod3134]

It's a Great looking craft. I think smaller vertical winglets may be needed below the main wings. The added stability at high speeds may be needed.

[@warushasoysa9902]

Guys this is awesome wish you all the best of luck !

[@jonahdrees9641]

cool work. very nice to see things falling into place

[@ammo193]

Well done, congratulations! The more you keep us updated the more exciting it becomes!! You guys make a great team and I wish you all the best 😊

[@spacedino1199]

Amazing work! I can’t wait to see it fly! ✈️

[@swealer]

F*ck yeah! Just finished the video you guys posted 8days ago and then i saw this! I am so pumped to see how it will all work out in the end! Keep it comin' boys! Great job so far

[@equenda]

Great project and great work, bravi! Just some advice: the fuselage over the jet exhaust looks fiberglass made (and rudder too). At +400KMH a fiberglass structure will broke for sure. So you need carbonfiber or metal rudder and fin. VERY IMPORTANT: you need a pilot with great experience with very fast jets. Anyway at 0.75 mach speed after 2 seconds of flight in straight line the model will be too distand and invisible. My last advice: don't be optimistic. All the best!

[@TheMachInitiative]

Thank you! There is a metal structure inside of the fin and rear nacelle - you can see us building it around ~30-60 seconds into the video we released before this one. We went for fibreglass over carbon fibre for radio transparency since our antennas are in the wings. We’ve used a combination of finite element analysis and experimental testing to size the structure and ensure it is strong enough. Got a great pilot lined up for the flight, with a lot of experience flying fast jets - we will take it slow with the flight tests!

[@yakacm]

Bit off topic, but wow, Bath looks amazing.

[@RockyShao22]

OMG congrats! Cooleset video I saw in quite a while on the whole internet, amazing work!

[@ohiorc5586]

I’ve been watching this concept for a year it’s so cool

[@ohiorc5586]

Also you need a lot less throw or you won’t have control, those straps are so funny and overkill, and your cg may change with those fuel bags. But overall awesome design I hope your 3d printed part wings don’t snap and I wish yall the best of luck. When you guys finish if this thing flies I may build a foam version flying model.

[@blueechodragon99]

Can't wait to see it fly!

[@daisywong-ke1kz]

This is so SICK! Looking forward to the next one. Also, we're thrilled to offer you some services, such as PCBs, 3DP or CNC, etc., if you need some of them for the upcoming project! (PCBWayDaisy)

[@TheMachInitiative]

Thank you! We would be interested in discussing further, do you have an email address we can contact you with?

[@torquedude]

This has been a fantastic build and looking forward to seeing it fly. Just double check your servo strength and control rod flex, the speeds yous guys are aiming for you need a lot of force to move the control surfaces. Great content as always and looking forward to the next one!……Rotorflex👍

[@Steve757-fl1hd]

Now that truly is a thing of beauty and an engineer’s dream come true. Intricate electrical work of art. Zooooooom!

[@domsui300]

This plane looks interesting. Even if many details do really look good and professional I would like to ask some questions to think about before your first flight. (I build and fly rc jet airplanes for many years now). 1. Who will be the pilot of this plane? It needs to be one of the best ans most experienced pilots in your country. The visibility of such a small plane will get extremely difficult as it will be like a little dot in the horizon in a few seconds after takeoff. 2. Other people mentioned already the servo trhrow / angle of elevons. Do use different flight modes for highspeed and low speed. the gyro must be adjusted to different speeds too. 3. Are you sure that the structure itself and the control surfaces are stiff enough to avoid any fluttering at high speeds. Wouldn't it be wiser to use balanced control surfaces at such enourmous speeds? As far as I know the gliders for dynamic soaring do have balanced control surfaces. I really hope and pray for you that it will be strong enough. I wish you good luck with this very difficult project and I hope to see a successful flight soon. (Sorry for my english) Best wishes from switzerland!

[@TheMachInitiative]

Thank you! In answer to your questions: 1. A professional pilot with two decades experience flying jets at up to 300 mph. 2. Yes - different flight modes on transmitter + controlling on the inboard elevons only at high speed. 3. Structure has been tested both experimentally and computationally. Thanks for your support!

[@domsui300]

So everything seems to be ready. 🤩 I wish you good luck! 👍

[@EleanorPeterson]

​@@domsui300- Your English is excellent! 🙂

[@wendyren]

Incredible work!!

[@cookingmaster6874]

HELL SON!!!!!! KEEP UP THE GREAT WORK!!!! HELL I LIKE YOUR PROJECT!

[@FrancisDrake-q3j]

Brilliant! Congrats on your turbine test! Can't wait to see it in the air!

[@stevenl.passalacqua3953]

Well done lads!!

[@prothomasgaming]

Very nice vid, btw, try to add an afterburner, those can double or even triple engine thrust. Looking forward for its maiden flight. Keep it up!

[@theangrydiver]

looks amazing, but you might want to add some heat shielding around the nozzle

[@StoneCBears]

Great job!

[@OMEGOOLIEBIRD]

Fantastic lads! I can see the same excitement I felt when doing the first start in the airframe. It truly is a great feeling after all the work! Like others have said in the comments and as I mentioned in my email, it is best to have double shear at both ends of the control rod... The elevon end is strong enough, but 100% I would want to see a clevice on the servo end, especially as you are using plastic servo horns, so there is the potential for them to twist. ANY flex at these speeds will bring an end to the project, so it is best to over engineer the control linkages. It would be good also to have a fairing to cover the control linkages and horns. Otherwise it is looking great! My regards to your proposed pilot, he is in for a hell of a ride!

[@TheMachInitiative]

Thank you! Really grateful for your support so far, it would be lovely to have another chat soon. We’ll fix the push rods - we thought ball jointing both ends would under-constrain the linkage (causing it to wiggle more) which was our reason for not doing it, we’ve been sternly proven wrong on this in the comments! The fairings will be used (as can be seen in our animation we released a while ago), we just hadn’t printed them yet.

[@OMEGOOLIEBIRD]

@@TheMachInitiative I would not ball joint the servo end, that can allow the servo horn to flex, as the load is applied offset from the centreline of the horn.. it may be OK on an aluminium horn, but not a good idea with a plastic horn. It is best to use a clevice, as this applies the load to the centreline and also holds the pivot in double shear, so there will be no flex.

[@TheMachInitiative]

@@OMEGOOLIEBIRD Sorry for the misunderstanding, we will get some clevices ordered. We've also got some aluminium servo arms on the way as well.

[@ammo193]

Yo Rupert!! Is it YOU that's going to be the test pilot they're talking about with all your fpv speed records, I'm sure you're up for it😁😁😁

[@MrNotStock]

Well done. I would be very interested to watch you and the team attempt this record again with 5yrs more experience. I think after 5years the knowledge and experience you gain will produce an impressive machine with high quality construction.

[@bakkerem1967]

I think you will need to plan for a few things : 1. A speed-proportional movement of the elevons. 2. Sanding down the surface as turbulence will decrease the performance of the elevons, especially at higher speeds. 3. Preparing for a switch to an aluminum skin at the tail. 4. I'm a bit worried about the fuel being in bags that way. They are crash resistant, but this may have consequences for the weight balance when they empty out. It might cause the craft to become less stable, when the bags are not secured and start slushing around in their confinement. Nonetheless it's an amazing project, honing your skills. I'd love to see the plane be able to be on display in one piece _after_ the successful record attempt though !

[@TheMachInitiative]

Thank you! Completely agree with all of this advice - we’re gonna velkro the bags to the inside of the skin to prevent them moving, and the internal tailfin structure is already aluminium - see our recent build video :) thanks for your support!

[@petercoffield9681]

Well done on the engine test and good luck for the flight test, just remember to take the flight tests slowly and don’t try to hit top speed on the first flight.

[@ButterLandingsGeoFS]

Awesome! Keep up the good work!

[@floschy_1]

You had two sides protected with a barrier but decided to stand basically right in front of the craft lol Exited to see this beast fly

[@BigDuke6ixx]

They only went to idle, but yeah, you never know.

[@floschy_1]

@@BigDuke6ixx 5:40, no they went full throttle once

[@BigDuke6ixx]

@@floschy_1 ok, never noticed. Not recommended due to stress on a stationary model.

[@dkjens0705]

My first time seeing a video about this project. Many good points in the comments. Those surface mounted elevon horns and nuts and long bolts are a no no. The servo arm linkages are an even bigger no no. Should be ball joints all around. The slightest flutter at high speed will rip that thing apart. That engine/fuse/wing cover looks very thin and flimsy, I suspect that will be ripped to pieces at high speed. For different elevon rates and positions at different speeds I can recommend consulting DSG pilots, they have some crazy split elevon positions for different speeds. Also, take a good look at how sturdy Dynamic Soaring Gliders, DSGs are built. They are built to sustain not only the ultra high G loads but the extremely fast air flow at very high speed. You may want to rethink that flimsy top wing and fuse cover, you're going to have a serious low pressure area there. It would make better sense to make to top more solid and permanent and enter the fuse and wings from below. Your control surface horns and linkages are so wrong. They will create so much drag and your throws look enormous.

[@finlayclarke347]

Best of luck i cant wait

[@elnikee]

How did you guys join the skeleton frame with the fibreglass hull? Some strong glue? Cheers and keep up the good work!

[@greghorine4995]

Congratulations on your successful ground tests, and best of luck on your future flights!!!

[@johngato737]

Motorcycle guy but, following! Love this

[@JP-ij6gf]

Damn impressive lads

[@oljobo]

Congrats! And… 2:34 Get a screwdriver Allen key with rounded tip for this work

[@sciekimike280]

Great job! I've noticed that the entire body of the aircraft it's made up of two main large pieces that come together for easier access and maintenance (ad that's great). My only concern is that at such elevated velocities any little unnoticed hole in the trailing edge may generate significant vibration and in worst case scenarios may lead to sever flutter. Also, consider a possibile redesign of the fuel tanks. The acceletations in this little aircraft can get very quick and may result in a shift in the CG. perhaps using aluminum may be a more complicated but safer choiche (?). That being said, wish you all the best!

[@TheMachInitiative]

Thanks for your support - the top panel will be glued down and sealed, we’ve not done this yet for easy maintenance!

[@BadmintonSkills]

So amazing 🎉

[@thegps7197]

Really good progress. You answers in the comments were very useful. You probably have enough thrust for takeoff, but jets have a similar issue with the intake size for supersonic flight, typically they have an additional opening intake for take off and landing to feed more air into the engine. Do you have any additional intakes to cool the electronics and allow air to flow between the engine and the cowling?

[@TheMachInitiative]

Yep - we have NACA ducts on the underside of the aircraft to cool the underside of the engine. The top half is exposed so has good airflow. We'll be improving the cooling of the avionics

[@thegps7197]

Nice. Can't wait to see the first flight

[@tetronaut88]

Count Binface is in Bath, do you think he'd like to see it? Anyhow, it looks amazing!

[@cadthunkin]

Cool looking plane. Interesting that you did not first make an electric ducted fan version to get used to flying the thing at 200 mph or lower. Dealing with the jet is so cumbersome compared to a switch. Once you fly a plane at 200 mph, you realize its hard to keep good visual on the planes position. Glider pilots have this problem and we give "test" input to see what the model does to infer its orientation (I do at least). You won't have time for that so I'll be curious to see how you handle that. FPV goggle might be the answer... My bet is it takes you four complete rebuilds to get to 400 mph.

[@TheMachInitiative]

We do have an electric ducted fan version: imgur.com/a/n5DhGXr Our pilot (who’s experienced with flying fast jets) will fly this EDF version in a couple weeks time - this will enable us to test out our catapult too. We also have a foamie which has already flown. The first low-speed flight will be line of sight, but we have an FPV system installed for when we go to higher speeds.

[@RCnerd74]

Look luck for the maiden👍

[@Aviator747a]

You need to make sure you have some "Reflex" built into you control surfaces as this is a flying wing. Also, static testing is great of your turbine with that intake duct is good. But, I would be static testing it with some simulated airspeed to make sure it will run properly. Heck even using a gas leaf blower into the intake would help. If that airspeed goes supersonic into the compressor, you will get compressor stall and then a flameout.

[@TheMachInitiative]

One step ahead of you on this! Tom tested the inlet + engine under varying crossflow conditions using two EDF’s to generate high-speed airflow. He was able to prove that the inlet won’t stall when exposed to 20 degree angle of attack air, or a side gust. You can see photos of the rig Tom used in this linkedin post: www.linkedin.com/posts/the-mach-initiative_it-has-been-a-busy-month-for-the-mach-initiative-activity-7176320516486553600-YimU?

[@Aviator747a]

@@TheMachInitiative Great to see the fore thought.

[@s737500]

The pushrod links on the servo horns is a no go, that is for sure. Get an rc jet guy to go over the plane before the first flight, or it will be short and expensive. Is the plan to glue the top surface on ? And if not, how will you seal the leading edges ?

[@wladimirreger3827]

It will blow on first full throttle, lets rain confety. To heavy, glass surface is to weak. Control horns are horrible, control ratio should be at least 1:3. Aelerons swing is way to high, you will need few mm on those speeds. Good luck for your pilot!

[@刘一成]

what was the maximum exhaust velocity？how did u measured it? btw great work, its a piece of art really!

[@TheBlueWizard169]

Great work 👏 ✈️

[@simiot1]

Cool vid! Is there bypass air coming out between the nozzle & nacelle? If not, that's gonna cause drag. I'm sure youse know that. I just thought it might be this way to stop the nacelle plastic from melting...

[@TheMachInitiative]

There is - thanks for your support!

[@oliverfletcher6707]

Very exciting milestone! I am curious however about the drag the control rods and horns could produce, it is complicated as the airfoil profile and the necessary torque from the servos may present a challenge.

[@AbabilOne]

It'd look cool if you guys did a shot inspired from the Darkstar scene in Top Gun when it comes flight time!

[@pegasusted2504]

Nice ;~) Good luck

[@neonuser456]

Great work!

[@iandavidson99]

That looks like a huge amount of elevon throw for such a fast jet. You'll need to dial that right back before flight

[@samgibson9153]

Great stuff and looking forward to seeing it in the air. Out of curiosity... Will you have flights modes as you get quicker? What elevon travel do you anticipate at full speed? I'm imagining only a mm or two? Will you have the resolution at speed to make very fine control surface movements?

[@TheMachInitiative]

Yes we will: For landing at 50 mph we need 15+ deg of elevon deflection to trim, which is the limiting condition on the size. You’re right about the sensitivity becoming an issue at high speed, to overcome this we’ve split the elevons in two, and at high speed we’re controlling using just the inboard elevons which are smaller in size, and also have a smaller moment arm. We’ll also have different transmitter modes to give the pilot more control in his stick movements.

[@EleanorPeterson]

Just wondering... Having chosen the name Kingfisher, had you considered using the bird's russet and electric blue colours? Kingfishers are famous (or notorious!) for only ever being seen as a blue flash that's gone before your eyes can focus on it. Seems quite appropriate for your sleek speed machine... 🐦👀

[@AnthonyDDean]

There's always a plus to everything... if your jet winds up in the back of your car during the test, at least you don't have to carry it to take it back home!

[@aryankaushik9373]

Amazing 🎉❤

[@bryanbilek2146]

Nice job. Thanks for the update !

[@eastdave2]

FYI, your flying control servo arm attachments are no fit for flying, I assume they are just for testing???

[@PricemoSC]

That is what I was about to say.. All the time/money, then this?

[@mirkomarko133]

Control horns.... inaceptable guys....🎉

[@madtinkerer]

This is so awesome! What FPV system are you using?

[@astralpx]

Sweet cruise missile

[@charlessampson6389]

Hopefully you are using a higher performance control link than the stock 2.4 module in that QX7. At the speeds you are aiming for you will exceed the control range of that radio in under 10 seconds. Would recommend looking at something like a 900mhz long range system that can provide multiple miles of control link range, as opposed to the default QX7 which you will likely start seeing failsafes before reaching 1 mile.

[@TheMachInitiative]

We have dual telemetry for redundancy. A 433 MHz system in one wing, and an 868 MHz system in the other

[@TomFly]

For landing you need to make sure that the plane cannot get off the ground again, once it has touched down. As it will be very fast, you need to keep it down. Look at the Dutch Speed Delta Teams and the constructions how they do it.

[@scottz143]

I wonder if there is a phenolic liner that you could place by the exhaust end of the turbine in between it and the fiberglass structure. Also I've seen fuel tanks from ww2 fighter planes that had some sort of sponge material inside the tank to prevent sloshing. (fuel cell foam) this might help with the sloshing issue.

[@valderja]

That setup with all those straps is very overkill. 😂

[@brianpentecostaldeplorable9841]

Better safe than sorry !

[@JonathanOfir-fs8oe]

Mach 0.75 that's insane

[@grumpyoldnerd8727]

well, you can get up to .71 Mach without an engine ;)

[@potatosalad68]

​@@grumpyoldnerd8727ingenious xDD

[@youknoweverything7643]

This is insane and i wosh o jad the knowledge and equipment to build a world record speed rc jet or plane or even build my own super fast jets put of carbon fiber. O just build balsa and foam planes from scratch but mostly balsa planes from kots and from just plans and cut my own parts. But i wish i jad tools to build a cool plane similar to this. I might start on one and slowly build it over a few years and see where it leads me lol

[@jayb2617]

as some one who flys rc jets i would suggest a training aircraft for your pilot if they dont have experience with fast turbine jets, if the take off is good it will get small very quickly and the control movments you have are very large hopefully they were just for testing! Glad i am not the test pilot it looks like it could go both ways, fast launching speed will be needed

[@eastdave2]

One other consideration, to set a speed record for a model aircraft you will need to engage with the FAI (Fédération aéronautique internationale)

[@BrianandLesley88]

You need to talk with the Dynamic Soaring guys who have been flying their R/C gliders close to 600mph for years. They might give you some tips on keeping that thing in one piece as the speeds increase.

[@TheMachInitiative]

Agreed - we’ve spoken a lot with rc jet pilots, but no one from the DS crowd. Its incredible what they do, would love to speak to someone if possible

[@rcplanebavaria]

I think it will explode before max speed. I wish much success. Hopefully the video will come soon from the flight ✈️

[@sUASNews]

Those servo links don't look strong enough, but that's only the looks might be wrong.,

[@williamhammond3998]

Glad to see you guys using Frsky equipment. The best choice for a serious project.

[@joshstroud6823]

its the least reliable system ????

[@grumpyoldnerd8727]

@@joshstroud6823 that would be Spektrum...

[@williamhammond3998]

@@joshstroud6823 You should give it a try and look into it. Frsky is the only system that uses a 900mhz and 2.4 signal simultaneously. The only other system that comes close in redundancy is Jeti. However jeti only uses 900mhz as a backup. I was a Spektrum user for years and it’s abundantly evident that Frsky is way more solid and reliable. You have to look past the people who negatively comment on a system they haven’t tried and are only trying to defend their choice in radio, which is clearly inferior.

[@superskullmaster]

Hope the finished model doesn’t have all that drag the control horn linkages will produce. That’s probably 50mph you could have with fairings.

[@TheMachInitiative]

The finished model will have fairings

[@viduraherath4008]

Are the bags just for testing? Since it looks like with purpose built fuel tanks, you could negate sloshing and also maximise internal area used for fuel storage.

[@HornetFlyer]

They need to get rid of any air in those bags, if they did that, no need for a UAT.

[@GregoryPolk-gz5bz]

So..which one of you guys is Chuck Yeager, and which one is Riddley.. Will be watching you all.."Chase that ol' Demon, to Mach 1".

[@echohunter4199]

Aileron lever linkage will generate a catastrophic vibration as the air compresses against them at high speed. The surface area is too large and I advise an in wing linkage design revision.

[@Murfster]

Super cool guys, congrats! What engine did you end up using?

[@TheMachInitiative]

Jetcat P300 Pro

[@N9197U]

@@TheMachInitiative seems like you're going to have about 134 propulsive horsepower at 760 mph, mach 1, that is a LOT!

[@flywithmike6904]

When can we expect a first flight!?

[@edwinthomas618]

Cleetus McFarland's scientific approach would have just thrown it up in the air wihhout all of this.complicated setup.😅. But seriously, great job guys

[@M14armorer]

I’m just waiting on the RTF version so i can fly it into the side of my house at Mach speed.

[@bornabarlovic3856]

Those connecting rods for servos only on screw or am i wrong ?? no screw through ?

[@HolyOllie]

please consider switching to ExpressLRS based control link. way more reliable than frsky.

[@grumpyoldnerd8727]

switching from a modern and licensed system to a bodged open source system in a project with such range would be a very bad idea. Flown line of sight you'd go for Jeti, BVLOS aka FPV you'd go for Crossfire or R9

[@tjm3900]

Apart from looking cool is there a reason that the overall design mimics that of a supersonic aircraft rather than that of a conventional high sub-sonic design like the Boeing or Airbus airliner ?

[@andrewfarrow4699]

Do you guys have any prior experience with RC jets or are you going to learn the hard way?

[@Zoey_the_Rat]

I wonder, are there some unique challenges in bringing an rc plane over mach 1 compared to a full size plane? Like, why hasn't it been done before?

[@TheMachInitiative]

Its not been done before because microturbojet engines generate ~4-5x less thrust relative to their size than the best full-scale turbojet engines. I think it is possible but you need to go into a dive at high altitude so that gravity is on your side!

[@59vijaiyaaravindthsr39]

can i know where the Cg is located ? and the location of Cp from normal position and the transfer location of Cp at its estimated top speed ? and i think the externally exposed control system of Aileron and flap will create significant parasitic drag at higher speeds ,limiting its topspeed!

[@iancommons9841]

You need to add a mode on the flight controller to decrease alerion deflection with increased throttle

[@TheMachInitiative]

Yep - we’ve got this + we will control only using the inboard elevons at high speed for even better sensitivity control

[@millycarrington]

@@TheMachInitiative No, you need to decrease control deflection programmed on airspeed not throttle position. If you were to throttle back quickly then you could easily have excessive control authority before the airspeed has bled off sufficiently and end up over controlling or inducing flutter.

[@smacfe]

Please go to a F3d race and talk to people who have experience in building and flying high speed aircraft.

[@TheYHoernchen]

I'm glad that the thrust of the turbine didn't tear the straps. I would have attached a truck to it just to be on the safe side. Honestly guys, how much thrust do you think this turbine develops? The weight and brakes of your steel test frame would have been completely sufficient. But all joking aside, on high-speed model airplanes you should ALWAYS control the rudders for tension, not for pressure as you solved it. This can have dramatic consequences, I would reconsider this design of the rudder linkage. You are smart people but you ignore the basic rules of speed flying. If you don't pay attention to this you will fail and I hope the first flight will take place somewhere in the desert without people! This is an ambitious project but I have the feeling that you don't really realize what kind of forces are at work at these speeds? Watch this video to get an impression of what it means to fly so fast and, above all, pay attention to the steering of the rudders! This is the right way. kzbin.info/www/bejne/eoGqdXSQrrZnas0

[@TomFly]

How do you want to launch the plane? Bungee?? Look how „Nils Herbrich“ does that. You find him on KZbin. ;-)

[@TheMachInitiative]

We had a call with Niels - great guy! We’re using a similar catapult method for our aircraft

[@Quatuux]

You could try to reduce the drag by removing the elevons horns entirely and using a system that is inside the wing. It's quite difficult to do with a thin wing, especially if you need wide deflection angles, but it could be doable.

[@ianturpin9180]

The world record speed for a RC plane is 548 mph. It is held by a dynamic soaring RC GLIDER.

[@andrewfarrow4699]

Those gliders explode in mid air when things go wrong. I don't think these guys have any idea of the scary dynamic loads at half the speed they are aiming at.