The biggest myth about split flaps

Рет қаралды 144,683

Күн бұрын

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
x.com/DarkAeroInc

Пікірлер: 402

@xpeterson 6 ай бұрын

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.

@ashlionell 6 ай бұрын

This is SO true. Gets my goat everytime.

@AM-hf9kk 6 ай бұрын

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."

@RobertCraft-re5sf 6 ай бұрын

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.

@timcross2510 6 ай бұрын

Hah!

@RobertCraft-re5sf 6 ай бұрын

@@timcross2510 Seems like a simple and reliable design to me.

@PetesGuide 6 ай бұрын

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!

@billcarrier9622 6 ай бұрын

It also eliminates any chance of control surface flutter.

@meazy451 6 ай бұрын

Oh thank God they were able to clear up your confusion.

@36thstreethero 3 ай бұрын

Turbulence (ride quality) was your biggest worry?

@PetesGuide 3 ай бұрын

@@36thstreethero no, efficiencies of their flap design was my worry. I incorrectly assumed this type would create more turbulence and thus drag.

@brianb-p6586 6 ай бұрын

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

@beverlychmelik5504 6 ай бұрын

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.

@kittycatpilot 6 ай бұрын

Also, the P-38 is another glaring omission.

@Matt_10203 5 ай бұрын

Modern airliners are using mostly slotted or double slotted fowler flaps.

@gwzipper1 6 ай бұрын

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!

@getinthespace7715 6 ай бұрын

I like that the design is optimized for being efficient at speed. no gaps, and as simple as possible.

@blakechinn5792 6 ай бұрын

Really happy you guys are staying simple with manual bar for flaps. Easier build, less failure points over time, simple.

@jeffpogue6962 6 ай бұрын

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.

@ammerudgrenda 6 ай бұрын

Better ergonomics too. No need to stare at the flap indicator.

@reubenmorris487 6 ай бұрын

@@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.

@Grarder 6 ай бұрын

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!

@user-um9sl1kj6u 6 ай бұрын

I agree. You just don’t see videos of people designing aircraft and telling you why. Usually you have to infer

@8literbeater 6 ай бұрын

Most Cessna singles have slotted Fowler flaps. --- 140A 150 152 170B 172 175 180 182 185 205 206 207 210 --- to name a few

@Thomipangang 6 ай бұрын

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!

@martinluton6513 6 ай бұрын

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.

@daviddavids2884 6 ай бұрын

air is Stationary wind tunnel testing is NOT conclusive.

@snorttroll4379 6 ай бұрын

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.

@Berend-ov8of 5 ай бұрын

@@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.

@Berend-ov8of 5 ай бұрын

The linkage is not a very elaborate design. Complicated sure, and fancy too, but not elaborate. Maybe somebody is running out of time.

@williamwilliam728 6 ай бұрын

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!

@slehar 6 ай бұрын

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.

@CafeenMan 6 ай бұрын

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.

@johnfitzpatrick2469 6 ай бұрын

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. 🌏🇭🇲🌲

@oddjobbob8742 6 ай бұрын

Like @PetersGuide your KZfaq 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 KZfaq.

@SuperYellowsubmarin 6 ай бұрын

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 !

@foesfly3047 6 ай бұрын

There is so much educational value in your videos ♠️

@jorgentoll314 6 ай бұрын

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.

@kickedinthecalfbyacow7549 6 ай бұрын

They do increase drag but they increase lift allowing the aircraft to fly at slower speeds without stalling, improving take off and landing performance

@jorgentoll314 6 ай бұрын

@@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.

@seanyounk1 5 ай бұрын

You guys are my favorite KZfaq 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.

@mirekslechta7161 6 ай бұрын

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.

@abel4776 6 ай бұрын

I would assume so, I would say their numbers are underrated "gentleman's agreement" numbers, should be friggin fast.

@985aviator 6 ай бұрын

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!

@usaerospace6707 6 ай бұрын

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.

@tomcoryell 6 ай бұрын

Congratulations on your build completion and flight. That’s quite an accomplishment!

@christopherpardell4418 6 ай бұрын

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.

@TheJustinJ 6 ай бұрын

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.

@user-it7lf7kk8m 6 ай бұрын

The Cessna 150 and 152 had Fowler flaps. The 150 will drop down to 40 degrees and is like a barn door

@kwaaaa 6 ай бұрын

Love the shared decision making process and explanation on the "why" about this channel.

@mosca3289 6 ай бұрын

This is a fantastic learning opportunity for all of us.

@shahramkhesareh8068 5 ай бұрын

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.

@matthewrank109 6 ай бұрын

this channel is top notch. what you all have built is so impressive

@LTVoyager 6 ай бұрын

My Cessna 182 had Fowler flaps. They moved rearward significantly before descending downward.

@TheJustinJ 6 ай бұрын

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".

@LTVoyager 6 ай бұрын

@@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.

@brianb-p6586 6 ай бұрын

@@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.

@doccls 6 ай бұрын

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.

@chrissugg968 6 ай бұрын

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).

@heartsky 6 ай бұрын

Always excited to see more DarkAero progress!

@selcukf 6 ай бұрын

This information was very useful for me. Thank you very much.

@genexplore 6 ай бұрын

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.

@jimboagogo 6 ай бұрын

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!

@therealaim-9xmissile 5 ай бұрын

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 😎

@jerrywatt6813 5 ай бұрын

,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 !😊

@R760-E2 6 ай бұрын

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.

@Patshes 6 ай бұрын

Get that thing flying!!!🆒😎👍!

@mitseraffej5812 6 ай бұрын

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.

@MurraydeLues 6 ай бұрын

DC3 had split flaps as well. Very informative video.

@dphuntsman 6 ай бұрын

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!

@MurraydeLues 6 ай бұрын

@@dphuntsman Plenty of photos of the DC3 flaps extended on the web. Unusual in they extended under the fuselage as well as the wing.

@jeffpogue6962 6 ай бұрын

I think it is just super cool that you share this with us all. Thank you.

@mirekslechta7161 6 ай бұрын

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.

@12345fowler 6 ай бұрын

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.

@quintusferrus3177 6 ай бұрын

Thanks for interesting information)

@CanardBoulevard 6 ай бұрын

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.

@w8stral 6 ай бұрын

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.

@jessechen4971 6 ай бұрын

@@w8stral The flap seems very light, will gravity be much help in this case?

@rnordquest 6 ай бұрын

@@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.

@w8stral 6 ай бұрын

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

@iforce2d 6 ай бұрын

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.

@desertpoj 6 ай бұрын

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.

@78779 6 ай бұрын

When will you fly? It seems like progress has been very slow of late. Can’t wait to see your fantastic aircraft airborne.

@mytech6779 6 ай бұрын

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.

@deansiracusa3966 6 ай бұрын

I’d always thought that split flaps just created more drag versus lift when extended. Thanks so much for this detailed explanation!

@Johnny-Too-Bad 6 ай бұрын

It's been a long time but the finish line is in sight.

@waywardscythe3358 6 ай бұрын

I'm excited for flight testing, and I'll be interested to hear how the flap deployment feels in flight.

@Relou4e 6 ай бұрын

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!

@billyk4711 6 ай бұрын

The most common Cessnas, like the 172 series use Fowler flaps, not slotted flaps. However, the Piper Cherokee series has slotted flaps.

@trespire 6 ай бұрын

Love the simple and elegant design. Design simplification is an art form.

@GWAYGWAY1 6 ай бұрын

I have always thought of most Cessnas having Fowler flaps as they extend as well as droop.

@electricalmayhem 6 ай бұрын

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

@brianb-p6586 6 ай бұрын

Yes, @@electricalmayhem, it is a short-travel design in those Cessnas.

@brianb-p6586 6 ай бұрын

This is good, and explains DarkAero's reasoning well. For a extensive overview of flaps, Wikipedia has a good article under "Flap (aeronautics)".

@daemn42 6 ай бұрын

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.

@frollard 6 ай бұрын

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.

@daemn42 6 ай бұрын

@@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).

@yellowrose0910 6 ай бұрын

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.

@dphuntsman 6 ай бұрын

Thank you for doing these!

@Dremekeks 6 ай бұрын

Interesting! Another composite plane that has a split flap is the TL-Sport Sting!

@bensmith7536 5 ай бұрын

what a brilliant overview of flap types, bravo.

@PatrickJWenzel 6 ай бұрын

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.

@rgt4848 6 ай бұрын

Awesome review. Thanks

@blancolirio 6 ай бұрын

Simplest fowler flap design Ive seen is on the Aviat Husky, which came from the Callair. Split flaps on the early C-310s.

@mirekslechta7161 6 ай бұрын

@tedsmith6137 6 ай бұрын

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.

@RubyRhod 6 ай бұрын

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!

@brianb-p6586 6 ай бұрын

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.

@brettharman8921 6 ай бұрын

great video, do you have an idea of the forces that the mechanism to lower and lifting the split flaps are experiencing?

@triedproven9908 6 ай бұрын

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.

@cabanford 6 ай бұрын

More videos please 😇

@rangefreewords 6 ай бұрын

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?

@paulking7019 6 ай бұрын

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.

@AC-jk8wq 6 ай бұрын

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. 😃

@daviddilley538 6 ай бұрын

Great discussion and Explanation…always thought split flaps were a simpler but cruder solution…and they’re not!

@gideonfourie8722 6 ай бұрын

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.

@jackoneil3933 5 ай бұрын

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.

@MarcinP2 5 ай бұрын

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.

@kiereluurs1243 6 ай бұрын

Enlightening explanation.

@semenkorolev8868 6 ай бұрын

What CAD are you using? Great explanations. Thanks a lot!

@Jazz3006 6 ай бұрын

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.

@N34RT 5 ай бұрын

It would be greatly helpful if you would specify the maximum split flap deflection for CL max.

@gaylegrove886 6 ай бұрын

Beautiful plane, best wishes to you for success. Just some thoughts. Your video shows a flap actuator attached only at the inboard, with no attachments or push rods along the span of the flap. I suggest looking at significantly beefing up (metal Plate) the flap control surface, especially in the zone where debris could be kicked up from the wheels into the flap control surface. perhaps a torque tube extending the length of the flap with multiple attach points. Also, if the flaps get stuck down, is there sufficient power and control authority to execute a go-around? If one flap control surface broke and retracted with the other extended, is there sufficient control authority to manage?

@Terrados1337 6 ай бұрын

thanks, very informative!

@billcarrier9622 6 ай бұрын

I've been wondering if you have a schedule to complete all outstanding air-frame tasks and get into flight testing.

@adjbutler 5 ай бұрын

I cannot wait to see this in the air!

@wallywally8282 6 ай бұрын

Well explained👍 This project seems like it’s been going on forever!

@ThomasTheTankEngine22 6 ай бұрын

Let's go! I've been refreshing your page everyday for the past week 😂.

@nathandavies2603 6 ай бұрын

Johnson bar for the win!! I strongly prefer manual flaps on a small plane like this.

@mirekslechta7161 6 ай бұрын

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.

@EricTheBlue2010 6 ай бұрын

Could you link the video your sampling the airfoil smoke demos? I've seen these stills before but can't find the source video.

@nevillecreativitymentor 6 ай бұрын

Dark Arrow SHINING BRRRRIGHT !

@johnmolli214 6 ай бұрын

With the single flap actuation lever at the inboard end of the flap, it sure looks like there will be a huge torsional load on the flap itself and very high forces on the single actuation arm and its related linkage. I would love to know what you have computed these loads to be.

@user-zl9hv9lu5n 6 ай бұрын

Guys, did you consider placing the torque tube coaxial to the flap pivot? In this case it seem to have more reliable mechanics. At least now if one of the links fail there would be differential lift created, which could be very dangerous obviously

@brianb-p6586 6 ай бұрын

They presumably want more mechanical advantage. In that design, the driving torque tube would rotate very little.

@torrunelade3004 6 ай бұрын

Looks good. Simple design 🔥🔥

@thescurry 6 ай бұрын

wow, great video!

@trumanhw 6 ай бұрын

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.

@CruizinEasy 6 ай бұрын

Aerodynamics for Naval Aviators supports your comments on flap types and their drag and lift charicteristics.

@Shazbat5 6 ай бұрын

Excellent.. By the time you are done, I'll be a fully accredited Internet aeronautical engineer!

@gregswank4912 6 ай бұрын

How much force does it take to engage the flaps at the appropriate flight speed? The angle of deflection on the flaps seemed to be similar to the deflection angle of the lever, which doesn't appear to give it much mechanical advantage.

@benjaminjohnson6476 6 ай бұрын

Im surprised you guys didnt mention the p38 as an example for fowler flaps

@buffdelcampo 6 ай бұрын

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.

@mirekslechta7161 6 ай бұрын

@cypher1o1 4 ай бұрын

Is there eventually going to be a flap indicator for the split flap similar to the spitfire since you cant see the flap position from the cockpit? Incase of malfunctions l.