The biggest myth about split flaps
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- čas přidán 14. 07. 2024
- Check out Xometry at www.xometry.com/darkaero
In this video, we dive into the details behind the decision to use a split flap design over other common options like the plain flap and how the mechanism for the flap system on the DarkAero 1 works. We also address some misconceptions that surround split flap designs, specifically around the drag they produce when deployed.
Additional resources on the lift and drag characteristics of split flaps vs plain flaps:
NACA Report No. 661: ntrs.nasa.gov/api/citations/1...
NACA Report No. 554:
ntrs.nasa.gov/api/citations/1...
NACA BOUNDARY-LAYER AND STALLING CHARACTERISTICS OF TWO SYMMETRICAL
NACA LOW-DRAG AIRFOIL SECTIONS: ntrs.nasa.gov/api/citations/1...
DarkAero 1 Aircraft - www.darkaero.com/aircraft
DarkAero Courses - www.darkaero.com/courses/
DarkAero Services - www.darkaero.com/services
DarkAero Apparel - www.darkaero.com/shop
If you enjoyed this video and would like to see more of this type of content, follow along as we work to engineer the fastest, longest-range aircraft you can build in your garage!
0:00 - Intro
1:34 - Flap Design Options
7:50 - Which has more Drag?
10:08 - How our flaps work
13:01 - What's Next?
More information on DarkAero can be found on our website and other social media accounts:
www.darkaero.com
/ darkaeroinc
/ darkaero-inc
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I love the ball park numbers you guys use. So many places shy away and just say “it depends on multiple variables” which I imagine is true but gives no perspective for reference or insight to the bigger picture.
This is SO true. Gets my goat everytime.
Agreed! So much better to say, "Hey we did the math comparing each of these under the same conditions, on the same equipment, and this is the result."
it's obvious that you guys are making this aircraft as simple and reliable as possible while also maximizing its speed and performance. Such an awesome plane.
Hah!
@@timcross2510 Seems like a simple and reliable design to me.
Within the first 20 seconds you cleared up my biggest worry about split flaps-the turbulence-without saying one word about it. Awesome storytelling and lead-in guys!
It also eliminates any chance of control surface flutter.
Oh thank God they were able to clear up your confusion.
Turbulence (ride quality) was your biggest worry?
@@36thstreethero no, efficiencies of their flap design was my worry. I incorrectly assumed this type would create more turbulence and thus drag.
It's interesting that the B-52 and B-29 are listed as examples for the Fowler flap, given that it normal practice for modern airliners that are much more familiar to viewers
Modern airliners have another variation of Fowler flaps with multiple elements and slots for the most part. Useing the B-52 is an example of a simple Fowler flap as drawn vs todays flaps.
Also, the P-38 is another glaring omission.
Modern airliners are using mostly slotted or double slotted fowler flaps.
You've got four potential failure points at the rod ends at either end of the two pushrods travelling aft from the main torques tube where, if you were to lose any of them, you'd risk ending up with a differential flap deployment - a catastrophic condition. One tube traversing from flap to flap with a single input pushrod would solve this. Same geometry in a side-on view, single centerline pushrod in a top-down view. Not sure if there is some other system taking the space that would otherwise prevent the cross tube at the flap hinge position, but I'd strongly recommend against the actuation configuration shown here.
Split flap concept though - I like your choices here!
I love your videos! So cool as both a systems engineer and an aero nerd to see the decisions being made and why. And the engineering explanations are just fantastic. Can't wait to see this thing in the air!
I agree. You just don’t see videos of people designing aircraft and telling you why. Usually you have to infer
I like that the design is optimized for being efficient at speed.
no gaps, and as simple as possible.
Really happy you guys are staying simple with manual bar for flaps. Easier build, less failure points over time, simple.
More enjoyable experience flying imho. I always love the manual flaps in the piper over the Cessna electric flaps as I continue to learn to fly.
Better ergonomics too. No need to stare at the flap indicator.
@@ammerudgrenda If you learn how the flap handle moves with relation to the detent, and how the airplane feels with different flap settings+airpseed+power settings, you don't have to stare at the indicator.
Thanks for adding in the extra clips from within the cabin!
Have a merry Christmas and a happy new year guys!
Hope to see this beauty flying next year!
Great video, you fixed my misconception that split flaps are more draggy than plain flaps.
I hate to be ‘that guy’ but the actuation linkage builds in the opportunity for a linkage failure to give asymmetric flap deployment. If you are able to put the torque tube on the hinge line of the flaps then you could have a single linkage from the flap handle to the torque tube rather than two, meaning that if any articulated joint in the system failed you would be left with a symmetrical failure rather than an asymmetrical one.
Please keep the videos coming, you’re doing incredible work.
air is Stationary wind tunnel testing is NOT conclusive.
smart to make the failure mode symmetric. let em know. this is the kind of stuff that next time will appear in an air crash investigation. they should fix it now.
@@daviddavids2884 You got things mixed up. Stationary air does not exist, which is the reason why wind tunnel testing does not conclusively simulate flying, but it's still usefull.
The linkage is not a very elaborate design. Complicated sure, and fancy too, but not elaborate. Maybe somebody is running out of time.
Soon this newborn will be taking its first flight. What a journey this is. Awesome engineering from you boys and good luck with the test flight.
Merry Christmas and a Happy new Year!
There is so much educational value in your videos ♠️
The Cessna flap is slotted when half way out, but Fowler fully extended. The slotted / Fowler flap is like a new biplane wing, tilted to catch the airflow deflected by the “upper wing” and deflecting it some more.
Merry Christmas Riley, River and Keegan from Sydney Australia. Thank you for your time and commitment to education. Each time I receive a Dark arrow video, I think... Holy sh#t and then: great it's learning time. Love the British spitfire flap info and "possible to manufacture split flaps"- in aluminium with ribs for strength.
Merry Christmas and peace of the lord be with you.
🌏🇭🇲🌲
You guys have put so much work and love and energy into this aircraft. I wish stuff like this didn't end up in bankruptcy most of the time.
Like @PetersGuide your CZcams answered a lot of questions. I would have guessed the slotted flap decreased efficiency by letting air slide up from under the wing. But as your “wind tunnel” illustration showed it does in fact improve the airflow and reduce turbulence.
Excellent work! Thank you for taking the time to produce this CZcams.
You guys are my favorite CZcams Channel. I think you are doing a wonderful job here of building a fan base to help launch the DarkAero 1. I have no doubt you guys will be very successful in time.
Another exemple of a fast light aircraft using split flaps is the JMB VL3. Also, some flaps are more easily mixed as flaperons to inmprove low speed handling, which is the important limiting factor besides stall speed and stall characteristic. Looking forward to first flight !
Interesting video! I guess it also comes down to deflection angles. Since you mentioned the Spitfire and Hurricane using split flaps, they had just two settings, either up or down and the flap deflected almost 90°. It seems to me that such large split flap deflections are more akin to speed brakes than lift devices.
They do increase drag but they increase lift allowing the aircraft to fly at slower speeds without stalling, improving take off and landing performance
@@kickedinthecalfbyacow7549 Yes, all flaps increase drag and lift. My point was that the split flaps on the Spit and Hurri seem to be more speedbrakes than lift devices due to the deflection angle.
This is a fantastic learning opportunity for all of us.
Fowler flaps: we have them guite often on ultralight airplanes in Europe, for instance Risen. In Italy they make the ultrafast two seat aircraft called Risen. Please note, with 100hp Rotax they guarantee the top speed at sea level 320km/h (173knots) and with turbocharged Rotax 915 -142hp they guarantee maximum cruising speed at 16 thousands feet 450km/h !!! (243 knots ) !!! Will Dark Aero be able to achieve the same velocity with much stronger engine ??? Risen has got the ultimate aerodinamics IMHO. Extreemly efficient and it is all carbon fiber too. What I like about Risen compare to Dark Aero, that Risen is not using any metal(aluminum) honeycomb, but rather materials which can never ever rust.... On the other hand what I like about Dark Aero is the gear(looks strong) and the 2 baggage compartments.
I would assume so, I would say their numbers are underrated "gentleman's agreement" numbers, should be friggin fast.
this channel is top notch. what you all have built is so impressive
This information was very useful for me. Thank you very much.
Love the shared decision making process and explanation on the "why" about this channel.
Always excited to see more DarkAero progress!
I thought most Cessnas have Fowler flaps not slotted flaps? Can’t wait to see this bird fly! I just finished my RV-6A a couple of months ago. First flight was an incredible experience! However the first flight of a new clean sheet design has to be the pinnacle of home building. Congratulations on your success so far!
I agree. The Cessna 172 flaps move down and back which increases the wing chord. Which is a Fowler flap. However, The 172 manual that I have refers to the flaps as the single-slot type.
Congratulations on your build completion and flight. That’s quite an accomplishment!
Nope. Just a slotted flap, which DOES move back and down, just not nearly as far. A Fowler flap is characterized by being RETRACTABLE in operation. Meaning a large section of it slides UNDER the top surface of the wing. To see one in operation just look out the window over or just behind the wing of any airliner during landing. Fowler flaps are usually accompanied by rather large fairings extending aft of the trailing edge to hold the complex tracking, linkage, and actuators that operate them.
In order for a slot to open, the flap has to move aft.
A fowler flap has the leading edge of the flap nearly reaching the trailing edge of the basic wing. It also translates aft a significant distance, without deflecting any noticeable amount. Where position 1 flaps is just an increase in wing area
Cessnas definitely deflect downward as much or more than they translate aft. Which at most might be 4-6" rearward. And the flaps trailing edge still remains within the basic wing planform as viewed from above, when fully deflected.
The Cessna 150 and 152 had Fowler flaps. The 150 will drop down to 40 degrees and is like a barn door
Most Cessna singles have slotted Fowler flaps. --- 140A 150 152 170B 172 175 180 182 185 205 206 207 210 --- to name a few
I have seen almost all of your videos and they make me glad and amazed,as making an aircraft needs to know several fields of science and knowledge's and you have all of them together.
Your job tells me that you were good students and are very qualified engineers now.
Congratulate.
Get that thing flying!!!🆒😎👍!
I like the mechanism attached to the flap itself especially. The geometry of it means that you're increasing the force you can apply to the flap as it extends further out into the airflow (and so would be harder to move manually).
DC3 had split flaps as well. Very informative video.
Are you sure? I’ve ever been up close and personal with a single DC-3- and it didn’t have flaps. Looking at photos of planes on the web, and I don’t see any indications of flaps- but, admittedly, all those photos are from the top, so for a split flap, wouldn’t see anything!
@@dphuntsman Plenty of photos of the DC3 flaps extended on the web. Unusual in they extended under the fuselage as well as the wing.
My Cessna 182 had Fowler flaps. They moved rearward significantly before descending downward.
Flap position 1 is 10 degrees deflection. It is the only flap position that extends the flaps trailing edge outside of the basic wing planform. At full 40 degrees, the flaps are definitely not projecting past the trailing edge. A true fowler translated the leading edge of the flap rearward to the trailing edge of the basic wing. Which is about 300% farther aft than a Cessna.
All slotted-flaps must translate aft to open the slot. As the slot gap has to remain about the same for each deflection angle, it cannot simply open more and more with angular deflection. It has to open the slot rapidly to its defined point before deflecting.
The proper technical term for Cessna flaps is "Slotted Flaps with Fowler Action".
@@TheJustinJ You are just making stuff up. The definition of Fowler flap is that the flap moves rearward as well as downward. There is no requirement that it move to the trailing edge of the wing. Slotted flaps rotate, but don’t translate. Fowler flaps translate and rotate. Cessna 182 flaps are Fowler flaps. End of story.
@@LTVoyager It looks like Cessna has used Fowler flaps (with rearward translation, although not much) since the 170B of 1952... and the same design continued through the 172 and 182.
Fowler and split flaps have one disadvantage which is the inability to use negative deflection in cruise. You have a good, simple and reliable design, well done!
One of the advantages of the split flap is that the separation bubble stably extends the pressure recovery aft of the airfoil trailing edge into the freestream, allowing the upper surface pressure to stay below static as opposed to having to recover to near stagnation. We (NASA) used this aspect to design a wing for a glider for Mars exploration; it was to be folded up in an entry capsule, then released to fall away and unfold. The flowfield conditions presented during pullout were challenging - transonic Mach and low Reynolds number. We found that a split-flap design maintained the high CL capability needed to achieve the pullout maneuver even under these conditions. Of course, the relatively high drag was also advantageous, as it would slow the glider and give more time for the pullout to occur.
I think it is just super cool that you share this with us all. Thank you.
One thing that's great about aero is that butt math and intuitions conceal the actual complexity of what's involved (leading to myths and misconceptions). I'm impressed at your guys' ability to condense these really complicated subjects down to something digestible and understandable.
As a pilot I much prefer manually actuated flaps. Have you done some design analysis on the mechanical advantage of your flap lever? It looks a little short compared to other aircraft of similar size I have flown with manual flaps.
Split flaps just need to be released and fall down via gravity, now the UP and REMAIN up/sealed with less drag is the actual problem. So springs etc are often employed here.
@@w8stral The flap seems very light, will gravity be much help in this case?
@@w8stralgravity will overcome the airflow? Ever try to open the door of a Cessna in flight or your car door while driving down the highway? I’m not so sure that would work.
Bottom rear half of airfoils have downward suction. I do not believe they went with a reflex airfoil so there should be downward suction. Now will they FULLY deploy? Nope. But flaps 10 or flaps 15? Yup. Spitfire flaps for instance fully deployed to Flaps ~20 with zero input from pilot other than: deploy. Where Cessna door is a compression zone. Same Cessna door on rear half of fuselage is a SUCTION zone and would auto open partially(one reason P51 was faster than Spitfire for instance. It dumped its higher pressure heat into a suction zone decreasing fuselage drag and decreasing drag of the radiator(p47) partially did this as well(though by default rather than on purpose). Cheers @@rnordquest
All this time I thought the purpose of wings was to provide lift, but there's actually a region of downward suction, amazing lol. And I thought that the purpose of extending flaps was to gain lift by deflecting more air, which should give an equal and opposite force on the actuating linkages, boy was I a dummy lol.
Thanks for interesting information)
Another aspect of the marvel that Concord was is that it had no lift augmentation devices at all, neither leading or trailing edge. Low speed flight was achievable because of the double delta wing, same as the Space Shuttle.
Riley's presentation was great. Although I don't usually get much fired up about the new composite airplanes, I wish you guys well on this venture (certainly no pun intended!)
I hope that handling qualities are as important as performance to you guys.
Working on getting my ppl and I dream to one day get a experimental kit aircraft and I’m definitely keeping my eyes on you guys! A zenith is cool but I’m honestly a low wing type of guy and I love the design, look, and performance of this aircraft. Keep it up guys 😎
,any decades ago I worked a lockheed with early composite materials and some I suspect are not open source as yet but I'm glad they are in wide use today so widely I always thought them quite amazing in testing !😊
It's been a long time but the finish line is in sight.
Thank you for doing these!
When will you fly? It seems like progress has been very slow of late. Can’t wait to see your fantastic aircraft airborne.
The most common Cessnas, like the 172 series use Fowler flaps, not slotted flaps. However, the Piper Cherokee series has slotted flaps.
Hi. One thing you mentioned was sealing. The gliding community have always been ahead in this area and use Mylar sealing and turbulating tapes. I have an 18 metre flapped Schempp-Hirth Ventus and it is sealed and turbulated within an inch of its life. A gliding buddy of mine has an RV in which he set various records in, including the elapsed time London-Cape Town-London record for a 200 hp aircraft. That is beautifully taped; everywhere! Have you considered what tapes you will use? I’ve attached a link to the first glider supplier I found. I live in the U.K. and have no connection with the company, but their site has a great selection for you to browse. Just a thought. My mate’s RV is impressively fast with a stock engine. But there’s not a gap an air molecule could squeeze through! I notice that the ailerons don’t yet seem to be sealed.
Fowler flaps are often on Ultralight aircrafts In Europe. For instance in Italy they make the ultrafast two seat aircraft called Risen with fowler flaps.. Please note, with 100hp Rotax they guarantee the top speed at sea level 320km/h (173knots) and with turbocharged Rotax 915 -142hp they guarantee maximum cruising speed at 16 thousands feet 450km/h !!! (243 knots ) !!! Will Dark Aero be able to achieve the same velocity with much stronger engine ??? Risen has got the ultimate aerodinamics IMHO. Extreemly efficient and it is all carbon fiber too. What I like about Risen compare to Dark Aero, that Risen is not using any metal(aluminum) honeycomb, but rather materials which can never ever rust.... On the other hand what I like about Dark Aero is the gear(looks strong) and the 2 baggage compartments.
I'm excited for flight testing, and I'll be interested to hear how the flap deployment feels in flight.
One of my biggest surprise when transitionning to the PA-28 Archer was my intstructor asking me to do a flaps up circuit and landing. He asked me at what speed I would fly the circuit and landing and I was all bent to say for sure faster than the regular speeds used traditionally. That's when he told me just fly the same speed as normal no need to fly faster just the attitude will be more nose up and power setting would be different. The "flaps enable slower speed" is really only true for the stall speed (a few knots of difference as per POH) but as you would never fly that slow anywhere in normal flight that wouldn't do any difference.
With a little change in geometry you could have gotten more leverage at the handle over the flap as it approaches full deployment rather than less. As it is, you have most leverage when it's not needed, and least when it would be nice to have. We do this on big heavy RC sailplanes to avoid breaking the servos when the flaps are fully deployed just in case we don't get them up before touchdown. For you it'll just be a matter of the flaps feeling really heavy at full deployment.
That was one of my thoughts - a 30cm deflection of the flap handle has to extend a relatively large chunk of wing into high speed wind. Gonna be tricky for sure to balance the forces with any possible spring assist.
@@frollard I'm not talking so much about the simple flap lever to flap angle ratio, but the way they've clocked the positions of each end of the linkage relative to each other. There are ways to set it so that you start with more leverage over the flap and end with less (control lever initially moves faster than surface, then slows down to match its speed) which is what they've done, or you can set their relative positions so that you start with less leverage (when you don't need it at low flap deflection) and gain leverage as you move it further (moving arm faster than flap).
Awesome review. Thanks
Let's go! I've been refreshing your page everyday for the past week 😂.
There is a great version of the legendary Libelle glider with those flaps. With the additional airbrakes it had a maximum descent angle of 1:4, strong ground effect and strong deceleration it was great to land on very short strips. I loved it!
I have always thought of most Cessnas having Fowler flaps as they extend as well as droop.
I’ve seen plenty of discussion about that online. We were taught they were “slotted Fowler flaps”, I think the manual only refers to them as slotted flaps. A quick google says the wing are increase is only just over 4%. I guess it’s one of those topics to throw into a group of pilots then sit back and watch the arguments lol
Yes, @@electricalmayhem, it is a short-travel design in those Cessnas.
what a brilliant overview of flap types, bravo.
More videos please 😇
This is good, and explains DarkAero's reasoning well. For a extensive overview of flaps, Wikipedia has a good article under "Flap (aeronautics)".
Great flap discussion. Just a minor nit: "The split flap comes out on top of the split flap when it comes to drag for a particular lift". The graph shows you mean the split flap has a better (ie lower) drag/lift ratio, so it's "on top" in performance, ie desired. However, the statement, especially if the graph were not there, could also imply the opposite: that the split flap has a higher drag/lift ratio (numerically "on top" of the simple flap) and thus is less desirable than the simple flap.
Interesting! Another composite plane that has a split flap is the TL-Sport Sting!
Love the simple and elegant design.
Design simplification is an art form.
Enlightening explanation.
Excellent video. I don't quite get to the "biggest myth" part, - I suppose it's the high drag assumption - but I love the factual nature of the presentation.
Aerodynamics tells me with the hinge point fixed at the front of the flap, when the flaps come down the trailing edge will effectively come forward thereby decreasing the mean chord. CoP will come forward (relative to CoG) reducing the relative moment arm and inducing a pitch-down tendency requiring nose up trim. That will be interesting to see confirmed during flight testing.
For fighter aircraft a lot of designs had maneuvering flap position so the split flap would be at low deflection and cause drag. Hurricane and Spitfire only had two flap positions - extended and up and predictably used split flap.
Interesting and informative explanations. You might consider getting rid of any background 'music' or soundtrack. It is really distracting, serving only to make it a little harder to concentrate on, and understand, the narration.
Krueger flaps. They increase camber too, like all other flaps. They just do it at the leading edge. This is not to be confused with things like Slats and Slots that do not increase camber. There can also be a hybrid Slat/Krueger flap. More types are probably out there that are only found on certain aircraft for unique circumstances or situations like flaperons. Ailerons that also function as flaps.
thanks, very informative!
I see most of what you are getting at, It depends on the intended type of field used by the aircraft. If you will always be at runways with nice clearways then you may only care about getting maximum lift to reduce touchdown speeds and reduce stress on tires and gear, drag can be modest.
If you plan on locations with steep final approaches to shorter runways, then energy management is more of a concern than minimum touchdown speed and adjusting drag is more important than lift.
A generally versatile behavior is for a small deflection to add some lift with minimal change in L/D (Maybe even a slight improvement over the clean wing.). Then as flap angle increases a rapid increase in drag relative to lift. (Gliders take it to the extreme of adding spoilers to the top of the wing.)
This doesn't require ideal flap behavior of course, as long as the flap design is "good enough" then the cruise and manufacturing concerns, that were mentioned in the video, become major factors.
There are a lot of wanna-be engineers out here on youtube, but you guys seem to really know your stuff.
You showed the pros and cons and your choice makes completly sense to me.
It would have been nice to hear an opinion why the big 2 choose fowler flaps for their big birds (I'm just a regular mechanical engineer for farm equipement; this topic is really interesting, but I have no idea what to make of all the possible choices).
again: great video! loved it!
Airliners need far more effective flaps with substantial chord extension and effective wing area increase to create viable configurations for takeoff and landing from a wing optimized for their cruise speed. The speed range of anything with a piston engine - even the DarkAero - is much narrower so less effective flaps are viable.
I cannot wait to see this in the air!
I noticed the projected rated speed of the aircraft will be around 230knots, will you need static whicks with this composite flap aircraft for less noise, interference in your electronics and in comms?
That was very informative. Did you guys do the load calculations on the flap surface area to see what amount of force would be needed to overcome wind resistance at say 150kt's worst case scenario? First thing I felt was the system needed more mechanical leverage on both ends of the long link. Very much so enjoying the whole thing btw.
Great discussion and Explanation…always thought split flaps were a simpler but cruder solution…and they’re not!
Well explained👍 This project seems like it’s been going on forever!
great video, do you have an idea of the forces that the mechanism to lower and lifting the split flaps are experiencing?
Juan Brown just mentioned on his latest video about the Lockheed at Chino that split flaps create drag and no lift. At least that's what I remember him saying.
Sees like high drag flaps would be desireable on an airframe this light and streamlined, it's always good to be able to get down when you want to
They have a split rudder so there is a little bit braking in the air, and you can control how much you want
Yes, the split rudder is intended to be used as a speed brake,@@minorlion1327. If drag is needed, it has the advantage of causing minimal pitch change... unlike the split flaps.
Two comments, 1) A big disadvantage to fowler flaps is the change in the center of lift. That can be mostly mitigated by adding leading edge devices. Of course that adds complexity but worth it on some aircraft. 2) Aluminum structure complexity can be greatly simplified especially for a simple part like a split flap by using a foam core and bonding aluminum sheets for skin. I've done this a lot and it's much more simple than a composite layup or molded composite part.
Fowler flaps are often on Ultralight aircrafts In Europe. For instance in Italy they make the ultrafast two seat aircraft called Risen with fowler flaps.. Please note, with 100hp Rotax they guarantee the top speed at sea level 320km/h (173knots) and with turbocharged Rotax 915 -142hp they guarantee maximum cruising speed at 16 thousands feet 450km/h !!! (243 knots ) !!! Will Dark Aero be able to achieve the same velocity with much stronger engine ??? Risen has got the ultimate aerodinamics IMHO. Extreemly efficient and it is all carbon fiber too. What I like about Risen compare to Dark Aero, that Risen is not using any metal(aluminum) honeycomb, but rather materials which can never ever rust.... On the other hand what I like about Dark Aero is the gear(looks strong) and the 2 baggage compartments.
Fowler flaps: we have them guite often on ultralight airplanes in Europe, for instance Risen(from Italy) , or Stream(from Czech Republic). In Italy they make the ultrafast two seat aircraft called Risen. Please note, with 100hp Rotax they guarantee the top speed at sea level 320km/h (173knots) and with turbocharged Rotax 915 -142hp they guarantee maximum cruising speed at 16 thousands feet 450km/h !!! (243 knots ) !!! Will Dark Aero be able to achieve the same velocity with much stronger engine ??? Risen has got the ultimate aerodinamics IMHO. Extreemly efficient(crossed Atlantic from Africa to South Anerica using 200l tank only) and it is all carbon fiber too. What I like about Risen compare to Dark Aero, that Risen is not using any metal(aluminum) honeycomb, but rather materials which can never ever rust.... On the other hand what I like about Dark Aero is the gear(looks strong) and the 2 baggage compartments.
Looks good. Simple design 🔥🔥
Excellent.. By the time you are done, I'll be a fully accredited Internet aeronautical engineer!
Nice update gents!
Does the center of lift move back when the split flaps are deployed? (A Mooney characteristic)
If no…. No trim change required with deployment.
If yes…. Trimming while deploying flaps at the same time and rate, is nice…
Safety opportunity…. Nothing worse than flaps accidentally retracting. Fast uncommanded retractions can be extra hazardous, as the stall speed may exceed the current airspeed without warning! (Hand slips off the handle, position lock not engaged)
Split deployment… is there a way that the flaps can accidentally deploy or not retract on one side and not the other?
A few minutes during the transition training should cover how best to use the flaps, trim, and what to avoid during slow flight.
😃
Is there a concern about the force required on that short handle to activate the flaps? Just looking at it has me a little concerned if there is an attempt to open the flaps at any relevant speed. (Even at a 50kt airspeed, there would be a pretty high torque because of the surface area of the flap.) It seems to me that this is also why most older aircraft I have seen with manual flaps have relatively long handles.
Dark Arrow SHINING BRRRRIGHT !
Aerodynamics for Naval Aviators supports your comments on flap types and their drag and lift charicteristics.
Simplest fowler flap design Ive seen is on the Aviat Husky, which came from the Callair.
Split flaps on the early C-310s.
Fowler flaps are often on Ultralight aircrafts In Europe. For instance in Italy they make the ultrafast two seat aircraft called Risen with fowler flaps.. Please note, with 100hp Rotax they guarantee the top speed at sea level 320km/h (173knots) and with turbocharged Rotax 915 -142hp they guarantee maximum cruising speed at 16 thousands feet 450km/h !!! (243 knots ) !!! Will Dark Aero be able to achieve the same velocity with much stronger engine ??? Risen has got the ultimate aerodinamics IMHO. Extreemly efficient and it is all carbon fiber too. What I like about Risen compare to Dark Aero, that Risen is not using any metal(aluminum) honeycomb, but rather materials which can never ever rust.... On the other hand what I like about Dark Aero is the gear(looks strong) and the 2 baggage compartments.
wow, great video!
What CAD are you using? Great explanations. Thanks a lot!
Johnson bar for the win!! I strongly prefer manual flaps on a small plane like this.
I've been wondering if you have a schedule to complete all outstanding air-frame tasks and get into flight testing.
I’d always thought that split flaps just created more drag versus lift when extended. Thanks so much for this detailed explanation!
I know by "deflection" you mean that the flap is angled downwards ...
However, I wish people addressed how it manipulates the airflow:
It must also deflect air as a lift source & can't just be pressure differentials.
Could you link the video your sampling the airfoil smoke demos? I've seen these stills before but can't find the source video.
When do you expect first flight
Great explanation guys,. Could you please reply with the anticipated load (lbs) at the flap handle during the clicks of extension? Thanks!!
Split flaps work via gravity, so it is usually either DOWN or UP. Force in question is just the weight of the flaps, so not much. Now getting them UP and sealed can require more force as aerodynamically suction is pulling them down on the trailing edge often. Can splitflaps do detents? Sure. Will DA do so? Who knows. Will they know exact forces? Not a chance, unless they did aero work. These guys do not have access to a wind tunnel and seem to do their aero work in CAD to get lower airfoil pressures(if they have done so). Now they should have a pressure polar of their airfoil if they look hard enough, but it would not surprise me if they do not have this either. This is often not published except as examples using say Clark Y airfoil for 12% thick@Re~1,000,000 They could actually use Clark-Y pressure polar as ~close enough though and it would not surprise me if this is EXACTLY what they have done obtaining forces + a large safety fudge factor. If much larger fighter sized aircraft can do it with just average pilots and MUCH larger flaps, and no mechanical advantage augmentation, It boggles the mind how this tiny aircraft would have flap stick forces worth mentioning. But then again, I have seen engineers completely botch simple into complex moronacy so... =)
Thanks!!
Thank you for the excellent synopsis on Flap types. Might you know if split-flap designs might be inherently different at high extension angles to Fowler design as far as L/D? I was reciently chatting online with other pilots about the how the early model Cessna 310s had a pronounced loss of lift (not stall) on landing if throttles were reduce below zero thrust, and the Beech Barons like the B55 model with Fowler flaps much less. Both were similar wing-area, airfoils and weights.
It would be greatly helpful if you would specify the maximum split flap deflection for CL max.
Interesting stuff.
In terms of slipperiness, the closest thing to your design I've flown is the Comanche (not that aerodynamically clean). With the Comanche I'll take all the drag I can get for descents. You are coming towards you destination at cruise altitude, say 12K feet. In the western US the airport is often located on the valley floor and surrounding hills limit your ability to descend early. You start your decent at say 500- 1000 fpm. But your air speed starts to approach VNE limiting your decent rate. You end up having to fly longer patterns aligned with the terrain to loose altitude. That sort of defeats the purpose of flying a fast plane to arrive sooner. Anyway, I wish the Comanche had drag devices I could deploy at higher speeds. The gear helps once you get slowed to a speed you can deploy it. but there you are again fly a fast plane slowly.