Improving lift on IRIS+ with other propellers

The all new IRIS+ comes with an upgraded motor as well as propellers versus the previous IRIS. While the new 920 kV motor along with the 5100 mAh 3S Lipo provides added lift of IRIS+ over the 850 kV motor of IRIS, this benefit is actually mitigated by the now shorter 9.5×4.5″ propellers. This means that while IRIS+ features a longer flight time than IRIS, the hover throttle (percent of throttle required to hover) is pretty much the same.

A loiter test flight with IRIS and gimbal and the new IRIS+ 5100 mAh battery shows a flight time of roughly 12 minutes and a hover throttle between 65% and 75% (See Figure 1).

Figure 1: Loiter test with IRIS on 5100 mAh battery

Figure 1: Loiter test with IRIS on 5100 mAh battery

The same loiter test flight with IRIS+ and gimbal shows a flight time of roughly 15 minutes but a very similar hover throttle to IRIS, at around 65% to 75% (See Figure 2).

Figure 2: Loiter test with IRIS+ on 5100 mAh battery

Figure 2: Loiter test with IRIS+ on 5100 mAh battery

This means that the flight time of IRIS did increase, but the lift performance did not. With the heavier setup of IRIS+ and gimbal, you are still at the verge of 70% hover throttle making your IRIS+ a “very underpowered copter” according to

If you ask yourself how this might happen with the new motors delivering higher kVs, look at the new self-tightening propellers that came with IRIS+. While IRIS came with APC 10×4.7″ SlowFly propellers, while IRIS+ features 9.5×4.5″ self-tightening propellers. These smaller length propellers basically reverse the benefits of the higher kV motors when it comes to lift.

The reason for the improved flight time can quickly be found by looking at the Ampere drawn during the flight. IRIS with the 850 kV motors draws more current during a hover test (See Figure 3). It is around 17-18 A.

Figure 3: Current drawn during flight with IRIS on 5100 mAh battery

Figure 3: Current drawn during flight with IRIS on 5100 mAh battery

During the same kind of hover test, IRIS+ with the new 920 kV Tiger motors only consumes about 15-16 A.

Figure 4: Current drawn during flight with IRIS+ on 5100 mAh battery

Figure 4: Current drawn during flight with IRIS+ on 5100 mAh battery

How to improve lift performance

Using the data for the new IRIS+ propeller in xcopterCalc confirms the measured hover throttle to be just barely under 70%. But let’s try to use xcopterCalc and calculate what the hover throttle would be if we mount the old 10×4.7″ propellers from IRIS on IRIS+. And indeed the expected hover throttle will reduce to about 57%, giving us much better lift performance.

In this post I will therefore show you how to improve the lift performance of IRIS+ by using 10×4.7″ SlowFly propellers.

Required materials and tools

The following material and tools are required:

How-to assemble

IRIS+ comes with self-tightening spin-on/off propellers, where the nut is part of the propeller. Also the motor mount shafts – the part that takes on the propeller – is either left or right threaded depending on the direction the motor spins. And last but not least the motor mount shaft on IRIS has a diameter of 5 mm, while the motor mount shaft on IRIS+ has a diameter of 6 mm. All this means that we cannot use the same nuts as we did on IRIS for mounting propellers on IRIS+. Here the DJI Phantom Prop Aluminum Alloy Replacement Nuts come to the rescue. They allow us to mount almost any propeller that will fit on a 6 mm motor mount shaft on IRIS+.

  • Use the 6 mm propeller adapter rings with your 10×4.7″ SlowFly propeller. Both for APC and HQProp this will be the largest ring in the set of 4 rings that comes with your propeller.
  • Mount the propeller on the motor. The propellers marked with “R” will go on the silver motor mount. These propellers will spin clockwise. The propellers without the “R” mark will go on the black motor mounts and will spin counter-clockwise. Press the propeller all the way down on the motor mount.
  • Place the DJI Phantom Prop Aluminum Alloy Replacement Nuts on the motor mounts. The silver nut will go on the black motor mount and the black nut will go on the silver motor mount.
  • Carefully tighten the nuts on the motor mounts, first with your fingers, then with the wrench that came with the nuts for the nuts as well as the wrench that came with your IRIS+ for the motor mount.

The final assembly of the 10×4.7″ propellers on IRIS+ can be seen in Figure 3 and Figure 4.

Figure 5: IRIS+ with 10x4.7" propellers (clockwise version)

Figure 5: IRIS+ with 10×4.7″ propellers (clockwise version)

Figure 6: IRIS+ with 10x4.7" propellers (counter-clockwise version)

Figure 6: IRIS+ with 10×4.7″ propellers (counter-clockwise version)

We are now ready to test our new propellers with either a Loiter test or a real mission. Figure 5 shows a Loiter test: Hover throttle is between 55% and 65% and flight time is also around 15 minutes.

Figure 7: Loiter test with IRIS+ on 5100 mAh battery with 10x4.7" SlowFlyer propeller

Figure 7: Loiter test with IRIS+ on 5100 mAh battery with 10×4.7″ SlowFlyer propeller

Note that you cannot compare the flight time in Figure 5 with the one in Figure 2 as I did not initiate the landing based on the same condition (voltage or mAh drawn).

Figure 6 shows an auto mission flown with IRIS+ and a full FPV kit (All up weight 1665g) on HQProp 10×4.7 Slow Flyer propellers. The mission continues beyond the 11 minute mark shown in the graph.

Figure 8: IRIS+ with 10x4.7" SlowFly propellers

Figure 8: IRIS+ with 10×4.7″ SlowFly propellers

Looking at the current drawn with the 10×4.7″ propellers, we can see that it is at around the same level as with the 9.5×4.5″ propellers (See Figure 9). The more “spiky” Amps curve is caused by slightly higher wind during this test than with the original props.

Figure 9: Current drawn during flight with IRIS on 5100 mAh battery with 10x4.7" propellers

Figure 9: Current drawn during flight with IRIS on 5100 mAh battery with 10×4.7″ propellers

The only drawback of using these 10×4.7″ propellers vs. the stock IRIS+ 9.5×4.5″ propellers is that they are not spin on/off propellers. It therefore takes a bit longer and requires tools to mount or un-mount the propellers.

But in return they provide you great lift capacity for the rather heavy IRIS+. Therefore after a few dozen test flights with 10×4.7″ propellers, I’m certainly not thinking about mounting the 9.5×4.5″ propellers ever again. I’ve flown the quad at  40 kmh / 25 mph in high wind and gusts at even 100 m / 300 ft altitude, without noticing any bad behavior.

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57 comments on “Improving lift on IRIS+ with other propellers
  1. jsolderitsch says:

    Do you need to change any PIDs in Mission Planner for using the old (larger) props with the Iris+ motors and battery? I have some old Iris props and I bought the nuts based on your recommendation earlier so once my Iris+ upgrade kit comes I can try this out for myself.

    • You might want to adapt the THR_MID value, but that’s it.

      • david ringler says:

        what about using tigermotors 2212-13 980kv on original iris with original iris props with new 5000lipo?

        • Christian Elsen says:

          That’s what you get with the IRIS upgrade kit: New Tiger motors 2212-13 980kv. The result is pretty much equivalent to IRIS+.

          • david says:

            Christian, I have the original stock iris I was asking about putting on my own tmotors 2212-13 980kv but with the iris to iris
            = upgrade kit they replace the 4in1 esc controller so is there anyway around replacing this? or can I just go in and write the new params as 3dr has you do when you install the iris to iris+ upgrade kit also they claim that you get lighter arms with iris+ upgrade kit?

          • Christian Elsen says:

            Yes, this will work. Although the new IRIS+ arms are lighter than the IRIS arms. You therefore don’t gain the weight loss due to the different arms.
            But your performance will nevertheless improve.

          • david says:

            IRIS+ COMES WITH 920KV MOTORS NOT 980kv!

  2. Peter van der pol says:

    Hi Christian,

    Thanks again for the clear explination of this topic.
    Is there a recommended proppellor for a 3DR Iris with gimbal and 4S 4000 MAH?

    Hope you can help me out 🙂

    Thanks in advance,


  3. Alejandro says:

    Wow, what a complete guide! Thank you. I’m buying all the bits n’ pieces right now.
    What was the total flying time with the larger props and full battery?

    • Flying time with the 10×4.7″ props vs. the 9.5×4.5″ props is pretty much the same. Compare Figure 2 and Figure 5.

      • Alex says:

        Have you tried to fun the IRIS+ with 2 batteries in parallel, zip tie the batteries to the bottom of the arms? with no gimbal and 10×4.7 props

        the weight would be around 1602g with 10200mAh
        Would that work to give you 24-30min of flight?

  4. fluffypony says:

    Christian, I have a set of RCTiger CF props lying around, their 10×3.3. I’m waiting for the DJI prop nuts to come in, but any thoughts on what the lower pitch will do? I’ve never been able to fully grok the whole pitch vs. motor KV vs. battery life thing;)

    • The 10×3.3″ props will most likely not provide you any benefit over the 9.5×4.5″ propellers. Simplified speaking, the pitch is the height that the quad would lift with one motor rotation if there wasn’t this thing called gravity (and to some extend friction). Therefore – again simplified speaking – higher pitch gives you more thrust. You can use to find out what effect different propellers have on IRIS or IRIS+.

  5. Nick says:

    Thank you for testing! Could you please post a graph of the power or current draw in addition to the throttle position of your flights?

    • chriselsen says:

      I added graphs for Current (Amps) for all three test flights.

  6. chris says:

    So does changing the props calculate to being able to lift 100g more than stock or is the payload limit still the same?

  7. Jan Lindberg says:


    I just received my first delivery of IRIS+ and have been test flying it for couple of times. I immediately noticed the same what you have come up and actually changed the propellers to Tiger Antigravity 10×3.3″. I fixed these by removing the propeller axle and mounted an extra “antigravity propeller plate” under the propeller and then the propeller and then again on top same plate. I actually installed one propeller already without the under plate, but as the prop is very close to the arm, I decided to do this and test it first like that.

    My initial feeling in general of IRIS+ is that its flying nicely and smootly, but lacks speed and trust. Compared to similar type copters like DJI Phantom 2 or SkyHero Little Spyder, IRIS+ seems to be very lazy in terms of how it reacts to gas. This is not a bad thing at all when you are doing aerial filming, but IRIS+ is clearly not a FPV “fighter” in terms of speed.

    This was just a first test flight, but flight time was just over 13 minutes. However, I did notice that at least IRIS+ radio telemetry showed strange battery voltage when I started, so I have to double check this and test it again. I do assume that the 10×33 is not ideal for this use, so I have to test again this with Gemfan 10×45 model props.

  8. brizey says:

    The 10X47 seemed to open up the iris+ a bit in stabilize.

    • Ricky Agrawal says:

      Do you have a link for the 10×47 props?

      • chriselsen says:

        The “Required materials and tools” section above lists two different kind of 10×4.7 props.

  9. Daniel Domit says:


    How does the iris behave in manual (STD) mode with this propellers? Is there any major changes like in the throttle position and stuff?

    Do you have to change any parameters to the software?

    Thanks a lot!


    • Christian Elsen says:

      As I wrote in another reply to a comment, you should adapt the THR_MID value, so that IRIS+ hovers at mid-stick position. I would probably start with a value of 580 to 600 and then fine tune during one test flight (Repeat the Loiter test above and see what you get for ThrOut, Shouldn’t be off by much).
      With that IRIS+ will behave in STD as it should be: With throttle stick in mid position it will keep altitude perfectly.

      • Daniel Domit says:

        Thanks a lot for your answer and this amazing guide!

        Sorry for all the questions, but if someone knows its you! :), do you know where I can find a 3d model to print prop guards for iris+?? I just found one for IRIS but i don’t think it works with IRIS+

        Thanks a lot!

        • chriselsen says:

          The IRIS prop guards should also fit on the IRIS+ as the arms didn’t change between the two models other than the material consistency.
          I have not used any prop guards and therefore can’t say how useful or not they are. If you are prone to damaging your props, I recommend to rather look for a flying field with more open space and to stay away from objects like trees, fences and light poles.

  10. Sergio Amateis says:

    Hi Christian, Thank you for your great and professional Post. Since I live in Italy and the items you suggest are in USA, please can you check if these will fit for modding my IRIS+ ?? (10×4.7 version)

    Thank you !

    • Christian Elsen says:

      With a propeller the first number specifies the length (in inch) and the second number specifies the pitch of the blades. With that the propellers you found on eBay match. But the form of the blade also influences the lift. And as these propellers don’t 100% match the ones that I fly, I can’t guarantee that they will work. But they look close enough, that you will most likely have an improved performance.
      The alloy nuts also nook good. But notice that they don’t come with the corresponding wrench. You therefore should already have a wrench, or buy it separately.

      • Sergio Amateis says:

        Hi, I finally ordered that props on Ebay and even if not specified, they are the HQprop you have pointed on
        I just want to signal this for other European IRIS+ users !
        Now I wait the nuts, to try the mod.

  11. Bill says:

    Thanks Christian! I have ordered the larger APC props. I have used this size on my FLIP FPV before and I am very happy with them!

  12. hfb says:

    Any chance you have tried 11×4.7 props on the Iris+ to see how those work out? I have some leftovers from a tri I had a while ago. You would definitely see a jump in current but I’m curious how everything else works out.

    • Christian Elsen says:

      Unfortunately propellers with 11″ diameter will not fit on the IRIS or IRIS+. The maximum size that will fit are the 10″ propellers highlighted above.

      • hfb says:

        Is that a physical limitation due to spacing? I don’t have my Iris nearby to check but I assume that’s why?
        Thanks for the quick reply and great blog post.

        • Christian Elsen says:

          Yes, exactly. That’s the physical limitation due to the spacing of the arms. You would either have to lengthen the arms or raise the motors so the propellers don’t touch the top hull anymore.
          Both cases would raise for me the question whether it’s worth doing these changes or not. Instead you might be better off building a new quad from scratch.

          • hfb says:

            Excellent. I figured as much. I was just trying to get a sense of if I could get away with using what I already have lying around. I have 2 of the 10×4.7 pusher props so I’ll just go pick up the complimentary two and be done with it. I should probably have spares too at some point.
            I’ve built plenty of tris and quads over the years. This is my go to for simplicity since it’s already set up so no sense to reinventing things.
            Thanks for the response.

          • david says:

            I AM LOOKING for someone with a vacumformer to make me a larger top or bottom body shell so I can use longer spacers so I can use a larger battery! for a bit longer flight times while keeping stock look! I have a tarot with 4114 320kv motors 15.5 props running pixhawkp4 40 minutes flight not hover real flying around!

  13. William says:

    Sorry if this is a double post, but apparently I didn’t accept the confirmation email in time.

    You are recommending 10×4.7 props by both APC and HQProp. I see that APC has RPM limits specified here: . According to that page, the APC props have an RPM limit of 65,000 / 10 = 6,500 RPM. Wouldn’t this be exceeded by the IRIS+ motors? 980 kV * 11.1 V ~= 10,900 RPM. They do indeed work as advertised and reduce throttle by ~10% on my quad while maintaining roughly the same amperage. However, now I’m terrified of the props flying apart. I’m new to the quad scene, so hopefully I’m missing something 🙂

    Thanks for your posts – they have been very helpful!

    • Christian Elsen says:

      Yes, you are right that in this setup the propeller is outside the RPM limits. But the same propeller was already used on the IRIS (non plus version) with a 850 kV motor (850 kV * 11.1 V = 9,435 RPM).
      After seeing that 3DR was selling a quad where propeller RPM are outside the manufacturer specs, I figured to give the above setup a try. And after a couple hundred flights I can’t find any issues with it. If you are really concerned about the low RPM specs of the slow-flyer props, you could also use E-props. They aren’t as good as the slow-flyer, when it comes to lift performance improvements, but they are rated for higher RPM.

      • William says:

        I guess I was being a bit overly cautious 🙂 If they’re good enough for 3DR, I’d say they’re good enough for me. I ended up going with HQProp 10×4.7, and they do give roughly a 10% lower Throut value for me as advertised.

        By the way – I found your blog after having a hard touchdown on a trip in the rockies at 11,000 ft. The IRIS+ (& Tarot 2D/Gopro) ran great for ~4 mins and slowly descended after that. I haven’t been able to get back up since then, but all my lower altitude tests are on par with yours and indicate I should at least get a few more minutes of flight time at that altitude.

      • Doug says:

        I have a set of APC 10×4.5 MultiRotor props lying around.

        Have you tested these. I would expect some improvement over the 9×4.5s the Iris+ came with.


        • Christian Elsen says:

          Yes, I also briefly tried APC 10×45 MR props. The performance was better than the stock 9.5×4.5″ props, but slightly less than with the SF props.

  14. erikgraham says:

    Great post. I’ll be filming in the Alps this summer between 9,000 and 12,000 feet.

    For aerial video, where vibration is the key factor, do you recommend the APC or the HQprops?

    • Christian Elsen says:

      I really like the HQ props and have used them in the last few hundred flights without any issues. I’m not sure how much their improved stiffness over the APC one really gives you an improvement in vibrations. I haven’t done a test-series on that so far. Might be interesting though.
      You might also want to look into Graupner E-Props, as they are even stiffer as the HQ props.

  15. Douglas says:

    Hello, I have a question, I buy HQProp 10 x 4.7 CW Propeller Slow Flyer – 2 Blade (2 pack) and HQProp 10 x 4.7 CCW Propeller Slow Flyer – 2 Blade (2 pack), or I should say one of the two to make the modifications that you indicate?

    • Christian Elsen says:

      Yes, you need a total of 4 propellers. Two clockwise and two counter-clockwise. As HQProp sells their propellers in packs of two, you need one pack with two clockwise props and another pack with two counter-clockwise props.

      • Douglas says:

        Thanks, I bought you recomendas propellers and hope soon to try the Iris +.

        Do you think of the batteries MaxAmps 5450 3-cell LiPo 11.1v Battery for 3DR Iris Quadcopter ??

  16. tonywaters says:

    I was thinking about three bladed 9×4.7. Anyone every tried a three bladed prop on the Iris+?

  17. Projectile says:

    I have been wondering about 3 blade and 4 blade Props myself @tonywaters. Been looking around to see if anyone has used spacers to raise the Iris+ motors for use of 11 & 12″ props, no luck yet.

    • David says:

      I purchased longer aluminum arms not cheap that let me use 15.5 folding props! now I want to use 600kv motors or even lower kv motors and working on getting a custom factory like body kit and install frame spacers for a 6s setup!

  18. Steve says:

    If you push or pry the nuts off of the stock props, you can grind off the 2 little tits that hold them to the prop, and use them with the 10/4.7 props. Just have to use a pair of pliers to tighten, but it works!

  19. Keith Wolters says:

    I have a set of H-Factor 2 Blade fold-able props that I tested the best I could and liked there performance. These are made for a Phantom but will work on the Iris+. Not only great for beginners but also a smaller package in a case. Christian Elsen…….If you are interested give me a shout on doing more testing on these. If you are in the lower 48 I would send you a set to try.

    • Tony says:

      I’m interested, what is the diameter/pitch on those?

      • Keith Wolters says:

        They measure 9.5 Dia. and appear to be the stock pitch. I could not find a pitch given. Made by Heli-Factor under new Phantom products.

    • Douglas says:

      Hello Keith Wolters, I’ve tried with Iris +, you could make a video of it.
      Thank you