I walk under this guy at midway airport all the time. I finally stopped to take a picture. I actually love how the holes look, but what are they for?
I walk under this guy at midway airport all the time. I finally stopped to take a picture. I actually love how the holes look, but what are they for?
In reply to Robbie :
It's a Dive Brake.
The entry in Wikipedia isn't long but basically they were/are used to slow the aircraft down in a dive so it doesn't hit Vne when pointed down at a steep angle to drop the bomb load.
But wouldn't the flap do that without the holes? Do the holes increase air friction or something else valuable?
The holes could be a way of maximizing drag for a given control surface area. A big honkin' air brake like you'd see on a modern fighter jet requires an enormous amount of power to actuate. They didn't have that much power to use on control surfaces back then, so the holes make sense as a way of getting a lot of drag out of a control surface that doesn't take too much force to actuate.
The flaps would change the pitch behavior. The dive brakes deploy above and below the wing surface to add drag but not pitch the plane nose down like flaps would do.
In reply to Robbie :
Here's a link to the history from US Naval Institute.
Even pilots of other services have a minimal understanding of dive bombing. All military pilots have put aircraft in vertical dives, and many have dropped bombs from a diving plane, but our Navy’s dive bombing was different from the diving attacks of conventional aircraft.
The unique features engineered into the Dauntless SBD enabled the pilot to fly a controlled vertical flight from 10,000 feet or more to sea level, tracking a moving target ship as small as 40 feet wide which was taking evasive action. Of these features most important were the split wing trailing edge perforated dive flaps or “brakes” to retard diving speed and allow more abrupt pullouts. Wings were strengthened to withstand the high G forces at pull out. A yoke was designed to throw the bomb clear of the aircraft’s propeller when the bomb was dropped in a vertical dive.
Ideally the dive bombing aircraft, in a vertical 90 degree attitude, plunged at a 70 degree flight path because of the remaining lift on the wings. The target, at 24 knots would travel 1,214 feet while a plane dived from a two mile altitude. Wind was also a factor. The aircraft was literally flown down the dive path at constant speed, using ailerons and elevators to continually adjust the point of impact until bomb release and pull out. Neither the Stuka nor the Val was designed for bombing with extremely high dive paths.(5) Instead of trailing edge split wing dive flaps their device was a flap that dropped vertically from the center of the wing spar. This also affected lift and the trim of the aircraft. As a result they were not as accurate as our Navy’s dive bombers without descending to lower altitudes.
Basically it allowed vertical descent without the number of problems that a solid brake would incur (IE make the aircraft more unstable.) Since most aircraft of this period had minimal mechanical assistance and lacked stabilization controls found in today's high performance bombers, attempting to control the aircraft as it descended like that was difficult as a huge number of minor inputs are necessary to keep it stable. These days we use computers with highly aerodynamically unstable designs to get that type of performance and still maintain control. It was more a rudimentary solution to obtain the performance.
That engineering also gave the Dauntless SBD a major advantage during Midway.
I wish I knew more about airplanes!
The0retical said:In reply to Robbie :
Here's a link to the history from US Naval Institute.
A yoke was designed to throw the bomb clear of the aircraft’s propeller when the bomb was dropped in a vertical dive.
Always wondered what that was for too! You can see it in the picture hanging between the wheels.
In reply to SVreX :
I wish I could find someone to hire me during the weekends to maintain WWII type stuff. I sort of hate that my A&P is going to waste now since I love that era of military aircraft (despite working more modern stuff for the last 7 years)
Northrop designed the SBD's forerunner. They discovered that solid dive flaps created buffeting in a dive. By perforating the flaps, top and bottom, it smoothed out the airflow allowing the SBD's pilot to make course corrections rather than wrestling the controls.
In reply to The0retical :
Go to the Warbirds Information Exchange or the Commemorative Air Force on the web. See if any restoration outfits in the area have volunteer days. They would love to have an A& P's help.
I believe the proper term may be "fenestrated"
Appleseed said:In reply to The0retical :
Go to the Warbirds Information Exchange or the Commemorative Air Force on the web. See if any restoration outfits in the area have volunteer days. They would love to have an A& P's help.
Thanks! I'll check them out. I used to do some on and off work for the guy that maintains a fleet of Stearman's at the local airport when I was fresh out of school. All I really want now is to keep my A&P current (not that there's really an enforcement mechanism but still.)
Just saw some videos about early naval aviation and an actual SBD pilot addressed this. The holes are there to allow a certain amount of airflow through the flaps to get to the horizontal stabilizer which would otherwise be in quite turbulent air. The SBD was known to be very stable in an attack dive. It's follow up, the Helldiver, wandered all over the place apparently, making it a bit of a nightmare trying to hit anything.
As you can see, it has the perforated flaps also, and a ridiculously large tail, which I am guessing was an attempt to solve the stability issue. You might also note that is pretty damn ugly also. Early ones where know to break in half on hard carrier landings!
oops
A potentially interesting note is that the dive flaps do not go all the way inboard on the upper part of the wing on the SBD, but do on the SB2C, maybe part of the stability issues.
The SB2C (son of a bitch, second class) was a mess. Partly because the Navy kept changing the requirements and the other part was because Curtis thought they were too big to fail and could foist whatever onto the military and they'd buy it.
By the time Curtis got around to solving most of the problems in 1944, Douglas' Ed Heinemann was designing the bird that killed the multi-seat attack aircraft, the superb AD-1 Skyraider.
Fun fact: When flying clean (no bombs on center or wing racks), the SBD had a wing loading that was nearly as low as the A6M (aka Type 00, aka Zeke), but had 300 more horsepower (though not the Zeke's power-to-weight). And was capable of pulling 9 gees, for more than 90* of turn, in a slight nose-down slice when starting at around 215 Kts or better, before speed fell below that needed to pull 9. Max sustainable in a level turn below 10,000 feet was around 4 gees. The Zeke's gee limit was around 5, past which the wings would self-destruct.
Who can tell me what the above figures would have meant, should an un-laden SBD flown by a sharp, aggressive pilot, have been attacked by a Zero. Gold internet star for the first correct answer (the is more than one correct answer here).
Well, there is an example of that happening. How about 3 Zeros vs and SBD? The SBD pilot was quite skilled and would break wildly when the zero made an attack to try and get into a firing position.
It was shown in the first season of Dogfights (episode 10):
The pilots name is Capt S.W. Vejtasa. You have to wonder what sort of mental state the rear gunner was in after that encounter!
Found it :
http://navalaviationnews.navylive.dodlive.mil/2013/05/09/swede-vejtasa-in-memoriam/
WildScotsRacingCampbellCougarSeed said:Fun fact: When flying clean (no bombs on center or wing racks), the SBD had a wing loading that was nearly as low as the A6M (aka Type 00, aka Zeke), but had 300 more horsepower (though not the Zeke's power-to-weight). And was capable of pulling 9 gees, for more than 90* of turn, in a slight nose-down slice when starting at around 215 Kts or better, before speed fell below that needed to pull 9. Max sustainable in a level turn below 10,000 feet was around 4 gees. The Zeke's gee limit was around 5, past which the wings would self-destruct.
Who can tell me what the above figures would have meant, should an un-laden SBD flown by a sharp, aggressive pilot, have been attacked by a Zero. Gold internet star for the first correct answer (the is more than one correct answer here).
It sounds like the SBD could come around behind the Zero but that’s too obvious so I’m concerned that…
The0retical
Should check out local museums too. They sometimes need aircraft mechs to keep the museum pieces in presentable condition. Sometimes they get "new" pieces that need assembly/restoration for display. Although that would be volunteer.
I really ought to do the same as what you want to do. My A&P is just doing nothing now. Problem is finding the time plus not a lot of opportunity where I am. Quite a few of us A&P's around here, most more current than I am.
mad_machine said:I believe the proper term may be "fenestrated"
The Martin Am-1 Mauler I believe had fenestrated, or finger flaps.
This is the flaps only setting, It provides additional lift and drag along with a nose down pitch that increases with speed.
This is the speed brake or dive brake setting. The upper surfaces increase drag, spoil lift and prevent pitch changes as airspeed increases
Appleseed said:mad_machine said:I believe the proper term may be "fenestrated"
The Martin Am-1 Mauler I believe had fenestrated, or finger flaps.
Fenestrated simply means "windowed" as in open holes. From Merriam Webster "having one or more openings or pores"
This has become such an awesome thread. Thank you GRM!!! Who knew the plane hanging up at midway airport was so cool?
I've never seen an article on the SBD referring to the flap holes as fenstrated, only perforated.
Our local air museum got one of these on long term loan from the Navy and restored it. Had a service history that included Operation Torch (the invasion of North Africa) and still carried some of the original markings. It was pulled out of Lake Michigan after allegedly running out of fuel and being ditched by a nugget pilot. When they got around to draining everything, the reserve tank was still, after all these years, 100% full. Pilot just forgot the reserve tank.
The restoration:
Before:
after:
If you're ever in SW Michigan, the Kalamazoo Air Zoo is well worth the trip.
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