Radjet 800

mankweemankwee Club Members Posts: 36

Why hobbyking has discontinued the Radjet 800 ???? It has no equivalent on the market!
Please bring it back !!!


  • Derek MayDerek May Club Members Posts: 16

    Just assembled the new plug and fly version. Few points to note - measure to the CG - it’s not where the picture in the instructions depicts. If the ESC setup does not follow the instructions try reversing the direction on the transmitter - certainly required for the Turnigy 9X. Personally I’d assemble with Foam Cure glue and just accept the longer cure time - it’s very difficult not to get the superglue everywhere!

  • icaro10icaro10 Club Members Posts: 10

    Derel May said:
    "measure to the CG - it’s not where the picture in the instructions depicts"
    So, is not to 383 mm from nose, not it is?
    Please, could you be more precisse?

  • icaro10icaro10 Club Members Posts: 10

    This morning I flew the Radjet-800 for first time, battery 3s 2200 fully backward.
    A sever pitch down moment behavior I was observed (nose down). Not easy to fly during takeoff.

    Taking into account my experience with the “SkySword 70mm 4S” I suspect that H-King planes are designing with wing loading too high and an inappropriate XCG location considering its own recommendations (battery without regards to its weight associated or space allocation available inside the plane).
    I recommend to H-KING:

    • Provide X neutral point location (No). Only depending of the aerodynamics, and fixed by aerodynamics calculation.
    • Stability margin recommendation by H-King (XCG-No), previously H-King must do fly test or aerodynamic simulation.
    • Less to pilot to fix the XCG considering mass distribution, battery constrains and space allocation plane to obtain the stability margin recommended.
    • Increase a little the wing loading (7-8 %), especially for cranked wing.

    With this recommendations, I hope that H-King will improve yours reliability, and clients its confidence.

    Best regards

  • icaro10icaro10 Club Members Posts: 10
    edited September 10

    - Increase decrease a little the wing loading (7-8 %), especially for cranked wing.
    I am sorry

  • icaro10icaro10 Club Members Posts: 10

    After my last comments about this plane, I include my recommendation of the center of gravity location concerning the Radjet-800 plane.
    XCG = 400 mm

    See file attached

  • Derek MayDerek May Club Members Posts: 16
    edited September 18

    Hi icaro10 sorry for the delayed reply but yes measure to the CG point - where the picture in the instructions shows is not the same as where it actually should be. My CG was too far forward on the first flight and I could not pull out of the dive after launch.

    I successfully flew yesterday but with the Turnigy 2200mah 3S 35C battery as far back as I can get it in the fuselage - quoted weight 185g - and I still had to put some lead weight at the back. Nevertheless I still think my CG is too far forward (still forward of the quoted 383mm from the nose) requiring 3-4 notches of up trim to fly level. So to not adversely increase the wing loading as you say I would buy a lighter battery to make trimming easier. The Zippy compact 2200mah 3S 25C is quoted as 22g lighter for instance.

    Did you find the aircraft fully controllable with CG at 407mm from the nose? I’m curious as to the potential CG range of the model.

    I also found it very sensitive in roll - more so than in pitch - although the latter is probably down to the CG being too far forward. So currently have the Dual Rates set to 40% on both elevator and ailerons - certainly worth considering for that first flight. Nevertheless I love how this flies - crisp, responsive and quick!

    Incidentally this might be old news but I found the adhesive lead strips you can get to trim golf clubs ideal to add weight to the rear of the aircraft. Landing was still at a reasonably slow pace.

  • icaro10icaro10 Club Members Posts: 10

    Hi Derek

    I am happy that you confirm my opinion concerning this plane. Three days ago it was my third attempt with a turnigy battery of 2200 and 188 g, placed as far back as the available space allocation of the plane allows and without adding any lead.
    A collage helps me for the takeoff launching. Plane tendency was to pitch down as usual, but trying pulling up the longitudinal stick, suddenly a wing rock the plane did, finishing the flight.
    Only once I have been able to fly this plane for now.
    Takeoff requires that the plane reach a high speed (I propose to Hobby-King an assisted takeoff device development). I have already bought two batteries of much lower weight, 1300 and 1550 mah respectively and I will center it at 400 mm from the nose next tima. I'll tell you.

  • Derek MayDerek May Club Members Posts: 16

    Hi Icaro my first flights were very similar! The first never pulled out of the launch dive but the CG was per the picture in the instructions and not measured, so probably 15 - 20 mm too far forward. Adjusting the CG back the second launch pulled out of the dive but then departed in roll and crashed. Ailerons were still set very sensitively so I suspect I encouraged a tip stall by too aggressive application of aileron - having also just self launched. Last flight was launched by a friend and into a decent headwind and flew well, albeit with 4 notches of up elevator trim - suggesting still nose heavy. Having applied lead to the rear I haven’t had a chance to fly again but I’m hoping the marginal increase in wing loading is negligible compared to the improvement in flight characteristics. It showed real promise as a quick, fun and solid performer on the last flight! 👍

  • icaro10icaro10 Club Members Posts: 10

    Hi Derek,
    After reading your appreciated comments, I confirm ours parallel experiences.
    Be careful with maximum TE elevon deflection (+/- 7 mm seems to be correct).
    Good loock Dereck! I am still worried.

  • Derek MayDerek May Club Members Posts: 16

    I’ll let you know!🤞 I’m away for a couple of weeks now but on my return - weather permitting - I’ll get it airborne again and we can compare notes 👍

  • icaro10icaro10 Club Members Posts: 10

    Unfortunately I confirm that the H-KING RadJet plane is a fraud intentionally or not.
    I attach below the reasons.
    In any case we should ask for compensation, or one clear explanation from HobbyKing/H-KING responsibles.

    RAD.jpg 34.1K
  • icaro10icaro10 Club Members Posts: 10

    Thinking on the world record of 100 meters is preserved by Mr Bolt with an average of 37.8 km / h, is logical to think the impossivblity to reach the speed required to launch such plane in reliable conditions.

  • Derek MayDerek May Club Members Posts: 16

    You sure your calculations are correct? I successfully flew it last week and definitely didn’t launch at anywhere near Mr Bolt’s pace! Sadly my Aeronautical Engineering degree was too many years ago now for me to accurately derive some of the data you have, but with all due respect the evidence of my flight would suggest to me that there is some error in your calculations somewhere?

  • icaro10icaro10 Club Members Posts: 10

    I am very happy for you Dereck. This morning I crached the plane definitely, as usual in takeoff manouver.
    We probably have similar ages and aeronautical education, and if you wish, I could provide you with the data that you suggest, and thus make me a cross-check concerning the table provided above.
    In any case, I only have one variable left, will we have the same thrust?

  • Derek MayDerek May Club Members Posts: 16
    edited September 25

    I'm sorry to hear that! What exactly happened?

    So I’m thinking with same battery, ESC, propeller the only possible variable is air density / density altitude based on either temperature / altitude or both affecting propeller efficiency. Nevertheless there should be insignificant difference in thrust produced to weight ratio - certainly not enough to make that much of a difference. It would have much more of an effect on wing lift than thrust produced in this case.

    I haven’t had the chance to fly mine again but last time even with what felt like a forward CG, we hand launched and flew successfully twice. Both times the landing was controllable, with motor off and at a fast walking pace, so an estimated 1-1.5 m/s or roughly 5 km/h (3.1 mph). So I’m struggling to understand the magnitude of your derived speeds?

    Incidentally foam cure glue is amazing to repair this - trust me I did significant damage in the crashes before these successful flights!

  • icaro10icaro10 Club Members Posts: 10

    Yesterday I spent time watching videos of YOUTUBE on this plane, and I have no doubt today that this plane flying correctly, but at the same time I do not understand what has happened to me with it. Therefore, I apologize to those who might have offended, mainly H-KING. It is true that I am not used to this type of aircraft, but I am a pilot with more than 40 years of experience. In any case, I will review my calculations, and I fear that the root of the matter was the non-ECS check.

    Sorry, in relation to your question, a colleague helped me to launch it, the takeoff was almost vertical, the path did not even become parabolic. No way give it another chance to this plane for me.

  • Derek MayDerek May Club Members Posts: 16
    edited September 26

    To me that sounds like the CG was behind the aft limit. Mine flew with the CG around 10 mm forward of where HK recommend. With the pusher prop the pitch up moment with application of power wouldn’t have helped you either if the CG was too far back. The friend who launched for me worked quite a few years in aerospace and was commenting that these types of deltas are very CG sensitive so I think half the battle is getting the correct weighted battery and the CG in the right place.

    I’ve been playing with RC on and off for over 30 years but when I started electric power didn’t really exist nor the high density foam, so you can now get incredible power to weight ratios and amazing performance. Sadly maybe my reactions are not quite as fast as they used to be or as I tell myself they are! 😉

    It’s definitely twitchy and for me the dual rates will probably stay at 40% for quite some time but wow it’s fast and fun to fly! I might also have to see what the heart rate monitor on my watch peaks at post flight! 😁

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