# How fast do dive bombers dive?



## cherry blossom (May 26, 2014)

OK! Time to admit my ignorance. Dive bombers had dive brakes to keep them from going too fast. So how fast did they dive?


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## Greyman (May 26, 2014)

I don't think dive brakes are effective enough to stop you from reaching your maximum permissible IAS.


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## Ivan1GFP (May 26, 2014)

I did a little reading a while back when building models of the SBD-3 Dauntless and the Ju-87B Stuka.
Simple answer is that it isn't the same with different aircraft.

The Ju-87 was a "True Vertical Diver" or something to that effect according to Captain Eric Brown. The Dauntless was not. The Dauntless typically dove on its target at an angle of around 70 degrees. From somewhat imprecise memory, the diving speed of the Ju-87 was around 350 mph and it had no trouble keeping the speed down. The SBD would do about 350 up to around 400 mph toward the end of its attack and DID have a bit of trouble keeping its speed down.

- Ivan.


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## FLYBOYJ (May 26, 2014)

Read the POH and it will tell you.


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## N4521U (May 26, 2014)

Just untill the skin peals off, then you should pull out!

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## stona (May 27, 2014)

The operational requirement for the Ju 87 B was that it should have a safe diving speed of 600 kph (373 mph). This was met with the B-1.

The normal vertical dive speed of all Ju 87 dive bombers was 350-370 mph.

Much research was done at the 'Kommando der Sanitatsausbildungs und Ersatzeinheiten der Luftwaffe' (Luftwaffe Medical Training and Replacements Command) in Berlin into the effects of g forces on aircrew using Ju 87s. This would prove valuable to other nations, post war.

Cheers

Steve


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## Wildcat (May 27, 2014)

The A-31 Vengeance would normally "sit" at around 300mph in a vertical dive with dive brakes extended. The airspeed would then build up to the 400mph mark when the bomb bay doors and dive brakes were closed for the pull out at 3000ft.


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## beitou (May 27, 2014)

What happens to the bomb after it is released? Does it follow the same dive angle onto the target, as the bombs aero dynamics are different from the bomber at some point it must surely change its path, is this taken into account when calculating the drop height?


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## davebender (May 27, 2014)

Luftwaffe doctrine allowed bombers to dive without dive brakes if enemy air defenses were too intense. This made bombing less accurate but increased survivability. Squadron leader got to make the decision.

Rudel mentions this in "Stuka Pilot".


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## stona (May 27, 2014)

davebender said:


> Rudel mentions this in "Stuka Pilot".



A thoroughly unreliable author.

The dive brakes enabled the Ju 87 to remain within its design limitations in a vertical dive. Without dive brakes I assume Rudel was implying that something less than a vertical dive, with a consequent reduction in accuracy, was used. Unfortunately for him a shallower dive exposes the bomber to greater, not lesser, hazard from anti aircraft fire.

Does Rudel recall that as Luftwaffe _doctrine_? It certainly doesn't appear in any other document I've seen relating to dive bombing tactics.

Cheers

Steve

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## FLYBOYJ (May 27, 2014)

Steve makes perfect points.

Gentlemen - regardless of what a pilot, any pilot may say, every aircraft has a specified Vne (never exceed speed). Exceed it and you could start bending the airplane and possibly kill yourself. Many of the aircraft mentioned here have flight manuals that could found in this forum. Look them up and examine what their Vne speeds are, your curiosity will be fulfilled! 8)

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## BiffF15 (May 27, 2014)

beitou said:


> What happens to the bomb after it is released? Does it follow the same dive angle onto the target, as the bombs aero dynamics are different from the bomber at some point it must surely change its path, is this taken into account when calculating the drop height?



Beitou,

Here is a short course in "aerial bombing". Forgive any glaring errors as I had this course in August of 1989. An aircraft with WW2 aiming technology (other than the Norden bomb sight) I believe used mostly an illuminated recticle with a center "dot" surrounded by several rings. The dot was a certain width, measured in "mils" but honestly don't remember the definition of a mil. Regardless, for a pilot to drop a bomb on a target his "butt" is required to fly over the target. What's meant by that is the aircraft must be flying a "course" that will take it over the target at the time the pickle button is pressed. Once the device leaves the aircraft it is effected by winds and will have a changing flight path on it's way down.

From the pilots prespective he will reach his roll in point, or perch, and start his dive. The preferred method is to roll in from a base (or roll in from a perpendicular heading to your target, I.E. it's in your 3 or 9 o'clock when you start), establish your aim point, which in reality is (from the pilots perspective) below the target. As the pilot / aircraft continues the target will march down your windscreen and hopefully at pickle altitude, on your dive angle, at your prescribed speed, with your aircraft completely in trim, you hit the pickle button with the target under your pipper (no wind). And, if miracle of miracles all that occurs your device will hit it's target (or at least with in it's lethal / effective) blast radius.

In reality there is always winds, and in combat someone will probably be shooting at you. In that case you as the pilot can do one of two things (aiming wise) and they are called mil crank or combat offset. Mil crank means you have some knowledge of the winds and will adjust your pipper to compensate for them. Combat offset (my preffered methond) means you or your flight leads briefs where they are going to aim for known winds, and if they don't audible something else you then correct off their bomb. That means if your lead says he is going to go pipper on at pickle, and his bomb hits at the targets 6 o'clock for 100 meters, then you compensate by putting your pipper at the targets 12 o'clock for 100 when you hit the pickle button.

Rules of thumb: If you are 1 degree shallow your miss will be greater than if you are 1 degree steep. If you are 1 knot slow your miss will be greater than if you are 1 knot fast. If you pickle 1 foot high your miss will be greater than if you pickled 1 foot low. The message to be gleaned from this is what we called tiger errors. Steep, fast, and press (going below pickle altitude) were MUCH better than the opposite. Also to be picked from this is that if you are a Stuka type aircraft, going straight down, it takes out a LOT of, or minimizes the errors in the equation!

To answer your questions, after release the "blivot" continues to impact, following a curve linear flight path (curved unless dropped from a 90 degree nose low attitude / perpendicular to the earth). The speed at pickle / release, the altitude, and if known the winds at all altitudes from pickle to impact, form part of the equation of it's flight and success. After you do it for awhile you learn what you historically drop (I dropped mostly short bombs or below the 3-9 line of the target A.K.A beginner bombs) and compensated for it. You also learn that steeper is better, never be slow at pickle, and press a little if you need to (tiger errors). It's fun to do (when no one is shooting at you) and usually the bet takes the better part of 20 minutes to brief (lots of quarters chaning hands in the debrief).

Cheers,
Biff

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## beitou (May 27, 2014)

20 minutes to brief and a lot longer for me to work through. Thank you a good post to explain bomb sightingand aiming.

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## Koopernic (May 27, 2014)

The dive bombing sites used interest me and I would appreciate it if someone shared information on them.

Initially Stuka's seem to have been aimed simply by diving vertically and lining up the target over markings on the nose. Latter elaborations included automatic pullout devices and a computing bomb site called the Stuvi 5B. The Stuvi 5B could be equipped with a mechanical computer called the BZA (bomb zeil automat) which allowed very shallow 'glide bombing' style approaches if forward visibillity of the aircraft allowed. Stuvi 5B computed the 'hit point' and continuously adjusted the recticle sort of like a gyro site presumably via a light collometer and deflection mirror. Bomb sites such as the Stuvi meant Ju 88 could shallow dive bomb without dive brakes. Incidentally the specified replacement for the Ju 87 Stuka was the Me 410 which included dive brakes, the Stuvi 5B as well as a glass window between the pilots seat.

The MK XIV bomb sight used on RAF heavy bombers could actually be used in dive bombing although the intention was clearly they be used in shallow dives. Towards the end of the war an attachment for the Norden became available to shallow dive bomb as well.

At some point radar altimeters entered the picture, I know they were used on the latter USN dive bombers which must have had elaborate dive bombing sights.

In the Osprey Book "Spitfire versus the V2" the dive bombing technique was to enter a 45 degree dive, aim at the target, then count off (10 usually) during the pullout and release the bombs. It's a bit of an odd book since no V2 site was ever disrupted but does describe the missions.

On German fighter bombers the ReVi (Reflex Visier) had an adjustable second rectical. The pilot aimed using the normal rectical and pulled up till the second reticule lined up and released. The second rectical was adjusted according to tables from speeds and altitudes of the planned attack.

A major advance towards the end of the war were the computing toss bombing sites being deployed by the Luftwaffe and USN. The Luftwaffe's TSA2-D the pilot aimed with his normal gun sight, then pulled up, a computer tracked the aircraft's movement using an accelerometer and released them at the appropriate point. Such sights can also release rockets and provide some standoff distance. The TSA2-D took in data from the gryros, airspeed, variometer, altimeter and if available the FuG 101a radar altimeter. The secret to accuracy however was the use of an accelerometer to track the aircraft during the pullup relative to the original line of sight. There is a myth around that the Me 262 would have made a terrible bomber, I suppose it came from Adolf Galland himself, but this bomb site would have made it an accurate delivery system.

Humans have an amazing ability to track and estimate 'ballistic' objects. Our ancestors needed this skill, the visual processing ability, to swing from tree limb to tree limb and at some point we used throwing objects to defend (like chimpanzees) and latter hunt using spears, rocks, arrows.

If developed through practice its quite accurate which is why dive bombing from 45 degrees or more was often effective. It seems to explain the male preoccupation with ball games.

Incidentally, the A-36 (P-51A with dive brakes) was apparently a true vertical dive bomber.

Hi BiffF15
"but honestly don't remember the definition of a mil"

My recollection from reading Walter Dornbergers book on V2 development is that he and von Braun promised 1 mil accuracy for the V2 (A4 then) which was 100 meters at 100km. The figure comes from Artillery and clearly means 1 part in 1000. They chose this number simply because it was twice as accurate as might be expected from the best canon shell. The way they promised to implement this was to use an electronic beam riding system with Doppler tracking of speed and transponder tracking of down range distance. The system was in about its 4th prototype form at the end of the war and known as 'voll zirkel' (full circle). The beam was extremely accurate, the problem was getting rid of (damping out) any residual velocities which caused drift.

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## Koopernic (May 27, 2014)

stona said:


> A thoroughly unreliable author.
> 
> The dive brakes enabled the Ju 87 to remain within its design limitations in a vertical dive. Without dive brakes I assume Rudel was implying that something less than a vertical dive, with a consequent reduction in accuracy, was used. Unfortunately for him a shallower dive exposes the bomber to greater, not lesser, hazard from anti aircraft fire.
> 
> ...



When Yamato was attacked by Helldivers vertical dives were used to minimize exposure to defensive fire as this minimised the exposed area of the aircraft. The defensive fire would have been coming from Yamato herself. However in the case of attacking land target AAA might more likely have been coming from the side of the aircraft from guns placed away from the targets itself. A steady vertical dive might help predicted fire.


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## RCAFson (May 27, 2014)

Greyman said:


> I don't think dive brakes are effective enough to stop you from reaching your maximum permissible IAS.



Theoretically, they should be. Apparently the dive brakes on the Barracuda were effective enough to keep the aircraft under the Vmax limit, but on the Sb2C, for example, increases in aircraft AUW meant that the DBs were no longer effective in keeping the speed under Vmax during a prolonged dive.


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## stona (May 28, 2014)

Koopernic said:


> When Yamato was attacked by Helldivers vertical dives were used to minimize exposure to defensive fire as this minimised the exposed area of the aircraft. The defensive fire would have been coming from Yamato herself. However in the case of attacking land target AAA might more likely have been coming from the side of the aircraft from guns placed away from the targets itself. A steady vertical dive might help predicted fire.



A shallow dive is equally predictable. It also takes longer. There is a high probability of defensive fire coming from the target, though of course it may well come from other weapons within range.

The biggest advantage of a vertical dive is an increase in accuracy. This was established originally by the Royal Flying Corps. After 'on the job' attempts during the war, the first recorded being by an S.E.5a of No.84 Squadron on 14th March 1918, extensive dive bombing tests were carried out by the British at Orfordness during 1918/19. 

The Germans went for a different ground attack system using armoured aircraft operating in 'Schlachtstaffeln'. The Germans did not dive bomb during WW1. The Ju K47 was developed for the ground attack role, though its inherent strength allowed it to be used for shallow bombing in 1927/8 and this has led to it being referred to as the grandfather of the Ju 87.

The doctrinal origins of the German development of dive bombing are long and various. Here I will just say that the dive bomber faction's attitude is summed up nicely by a directive from General Kurt Freiherr von Hammerstein-Equord, in 1932 when he was Chief of the Army High Command (I think, haven't checked date). Air defence and air combat forces were to be considered solely as_ "auxiliary weapons of the army and navy."_

Cheers

Steve


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## pbehn (May 28, 2014)

Can someone explain how diving vertically on a target reduces the bombers vulnerability, I would have thought it was the opposite, just askin'.


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## stona (May 28, 2014)

It minimises area and time exposed to the target.
The dive bomber is most exposed to fighter and artillery on approach (when the FAA fighters in the Med attempted to disrupt their formations and hence bombing accuracy for example) and, particularly to fighters, as they reassemble at low level following the attack.
Steve


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## Greyman (May 28, 2014)

RCAFson said:


> Apparently the dive brakes on the Barracuda were effective enough to keep the aircraft under the Vmax limit



Not according to the Pilot's Notes ...


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## tomo pauk (May 28, 2014)

pbehn said:


> Can someone explain how diving vertically on a target reduces the bombers vulnerability, I would have thought it was the opposite, just askin'.



Most, if not all AA guns were unable to be elevated more than 85 deg. The manually-operated guns were also pain to accurately train at really high angles, due to human anatomy. The near-vertical dive should allow for almost 10 deg wide cone where target's AAA would not present as much as a threat as shallow dive, let alone a slow and low level approach as done by most torpedo bombers.


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## RCAFson (May 28, 2014)

Greyman said:


> Not according to the Pilot's Notes ...



Maybe I missed something but I don't see anything in the Pilot's Notes to that effect. The Secret Years, p.294 states:



> ...PI767 was delivered to
> Boscombe in October 1941 (Merlin 30), weighed 12,820
> Ib with a 1,5661b torpedo, and completed handling during
> which it was found impossible to achieve more than 330
> ...



P1767 was lighter than the later models, but the speeds recorded were still well under the permitted limits. During the later tests P1767 had been modified to Mk II standards and was somewhat heavier and recorded 280mph in the dive (as noted above).


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## stona (May 28, 2014)

tomo pauk said:


> Most, if not all AA guns were unable to be elevated more than 85 deg.



Many of the RN's destroyers were using their 4.7" guns as 'anti aircraft' guns, and well into the war too. These had a maximum elevation of 40 degrees making a vertical dive bomber almost invulnerable.

Cheers

Steve


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## RCAFson (May 28, 2014)

stona said:


> Many of the RN's destroyers were using their 4.7" guns as 'anti aircraft' guns, and well into the war too. These had a maximum elevation of 40 degrees making a vertical dive bomber almost invulnerable.
> 
> Cheers
> 
> Steve



SOP for most ships was to engage dive bombers with predicted fire while they were flying level prior to the dive and then switch to "barrage fire" when the aircraft went into it's dive. Barrage fire entails firing shells to burst above the target ship so that the dive bombers must fly through the bursts as they descend to their bomb release height. 40 deg elevation guns could participate in predicted fire (depending on range and target altitude) and barrage fire.

Predicted fire (guns controlled by an AA firecontrol computer) was almost impossible against diving targets, because of the short times involved prevented computer solutions and the complex geometry made target tracking too difficult. Assuming the target ship's guns could elevate sufficiently, the target would typically be engaged with barrage fire, or local controlled aimed fire.


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## stona (May 28, 2014)

Barrage fire is all well and good, but with an elevation of only 40 degrees it might be ineffective against dive bombers approaching at a typical 9,000-12,000 feet as the RN found out when the Luftwaffe went after Illustrious.
Cheers
Steve


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## FLYBOYJ (May 28, 2014)

RCAFson said:


> Maybe I missed something but I don't see anything in the Pilot's Notes to that effect. The Secret Years, p.294 states:
> 
> 
> 
> P1767 was lighter than the later models, but the speeds recorded were still well under the permitted limits. During the later tests P1767 had been modified to Mk II standards and was somewhat heavier and recorded 280mph in the dive (as noted above).



What does the pilots' notes say??? That the only real and official source for this discussion.


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## RCAFson (May 28, 2014)

stona said:


> Barrage fire is all well and good, but with an elevation of only 40 degrees it might be ineffective against dive bombers approaching at a typical 9,000-12,000 feet as the RN found out when the Luftwaffe went after Illustrious.
> Cheers
> Steve



Illustrious had 80 deg elevation on her 4.5in guns. Her accompanying destroyers did engage the attackers with predicted fire and barrage fire, but as during many of the Pacific war carrier battles, a determined DB attack will get through.
View attachment 225534


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## RCAFson (May 28, 2014)

FLYBOYJ said:


> What does the pilots' notes say??? That the only real and official source for this discussion.



Pilot's notes (Feb 1945) state that the IAS Vmax during a dive is 315 knots or 260 knots with dive brakes; the earlier editions state the same.


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## FLYBOYJ (May 28, 2014)

RCAFson said:


> Pilot's notes (Feb 1945) state that the IAS Vmax during a dive is 315 knots or 260 knots with dive brakes; the earlier editions state the same.



Then that's the real source. BTW there's a copy on this site.

http://www.ww2aircraft.net/forum/ot...tech/upload-pilots-notes-barracuda-25827.html

I believe the dive brakes will keep the aircraft at Vmax providing you're working within the parameters of the pilot's notes (2,000 rpm). Beyond that it's questionable as it would be in any other dive bomber of the period.


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## Shortround6 (May 28, 2014)

For AA work from ships please remember that the ship is rolling and/or pitching while at sea (out of harbor) which is going to have some serious effects on high elevation fire. Training is also a pain the arse. You want to move the gun barrels just a bit to the left even at 80 degrees? you have to change elevation as the gun mount rotates to keep the guns pointed near the same point in space. 

The US 1.1 gun mount was specially built to combat dive bombers an could slew the guns 15 degrees either way independent of training the mount.







Note the gear rack and pinion that allows this.


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## FLYBOYJ (May 28, 2014)

RCAFson said:


> on the Sb2C, for example, increases in aircraft AUW meant that the DBs were no longer effective in keeping the speed under Vmax during a prolonged dive.



I pulled a flight manual for the SB2C-5 (AN 01 25AD-1) and there's nothing that specifies that, although there's also no section of flight limiatations. There are dive angle charts at the rear of the document that provides airspeeds based on weight, configuration and dive angles, again, nothing addressing DB effectivness.

AN 01-25AD-1 Prelininary Pilot's Handbook of flight operating Instructions SB2C-5 Airplane


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## stona (May 28, 2014)

And the predictive fire was limited by the predictive abilities of the fire control system. We know how well the RN's systems worked against aircraft diving at over 350 mph at 80 or 90 degrees. Illustrious was equipped with more modern equipment and I guess others in the task force (Warspite, Valiant?) were too. I have no idea how her close escorts like Hasty and Jaguar were equipped. It didn't stop Illustrious being reduced to a floating liability in six and a half minutes.
Cheers
Steve


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## RCAFson (May 28, 2014)

stona said:


> And the predictive fire was limited by the predictive abilities of the fire control system. We know how well the RN's systems worked against aircraft diving at over 350 mph at 80 or 90 degrees. Illustrious was equipped with more modern equipment and I guess others in the task force (Warspite, Valiant?) were too. I have no idea how her close escorts like Hasty and Jaguar were equipped. It didn't stop Illustrious being reduced to a floating liability in six and a half minutes.
> Cheers
> Steve



Can you name any dive bomber attack on a carrier that was stopped by AA? NO WW2 AA system had the capability to defeat a determined DB attack, even with considerably larger numbers of defending ships than were present when Illustrious was attacked.


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## Greyman (May 28, 2014)

FLYBOYJ said:


> I believe the dive brakes will keep the aircraft at Vmax providing you're working within the parameters of the pilot's notes (2,000 rpm).



What makes you say that?


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## FLYBOYJ (May 28, 2014)

Greyman said:


> What makes you say that?



It's in the pilot's notes - para 42 p16 - you start your dive with a power setting of 2000 rpm. It gives the entire process for diving and seems to be revised for the March 1943 issue we have posted in the technical section of this site.


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## Greyman (May 28, 2014)

Right, but why would you come to the conclusion that the maximum permissible diving IAS they list is 'the speed at which your aircraft will stay provided you keep your engine settings as prescribed'?


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## FLYBOYJ (May 28, 2014)

Greyman said:


> Right, but why would you come to the conclusion that the maximum permissible diving IAS they list is 'the speed at which your aircraft will stay provided you keep your engine settings as prescribed'?



Because at that given RPM you are not going to build up speed to exceed Vne or Vmax. Remember the aircraft has a constant speed prop that will act like your transmission when you downshift while going down hill. You also control speed by how far you lower the nose in the dive. if you go to the pilot's notes it provides all the parameters and in theory if you follow these instructions there should be no issues in operating this aircraft.


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## CharlesBronson (May 28, 2014)

> The US 1.1 gun mount was specially built to combat dive bombers an could slew the guns 15 degrees either way independent of training the mount.



Interesting detail. 

-----

A forgotten divebomber of ww2 is the A-36 Apache or Invader, being basically a converted fighter I guess its vertical bombing speed should be very high. And *yes*... the dive brakes are precisely made to avoid the aircraft to achieve terminal speed.


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## FLYBOYJ (May 28, 2014)

CharlesBronson said:


> Interesting detail.
> 
> -----
> 
> A forgotten divebomber of ww2 is the A-36 Apache or Invader, being basically a converted fighter *I guess its vertical bombing speed should be very high*. And *yes*... the dive brakes are precisely made to avoid the aircraft to achieve terminal speed.


Maybe, maybe not - look in the POH. I'm on the way out, I'll engage later.


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## FLYBOYJ (May 28, 2014)

I looked at the POH posted here, it's incomplete and does not show flight limitations. According to internet sources, max dive speed was 390 mph

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## Greyman (May 28, 2014)

FLYBOYJ said:


> Because at that given RPM you are not going to build up speed to exceed Vne or Vmax.



I don't think that's how it works, but my knowledge of engines and propellers isn't the greatest so I'll leave it to the more knowledgeable folks.

Interestingly, with regards to the pilot's notes, the Barracuda I, II (Merlin 30 32) are as you describe, but the Barracuda II III (Merlin 32) notes give no mention of RPM, but say the dive should be entered with not less than +6lb./sq.in. boost to avoid gaining excess speed.

This indicates to me that the reason for the 2,000 rpm is due to a propeller damage/overspeeding issue: the smaller pitch range on the 3-bladed prop compared to the 4-bladed, 32 degree prop.

All this aside - in reading A&AEE dive bombing tests with the Barracuda II (merlin 32) the aircraft could be dived to 300 IAS with brakes deployed, 2000 rpm and 0lb boost.

A telling bit in the 'conclusions' of the report:

_The limiting diving speed was reached in a near-vertical dive (entry being effected by a firm push force on the control column) after diving through 4000-5000 feet, and hence, if a steep diving technique is to be employed operationally, the height at which the dive is entered must not be more than 5000 feet approximately above the required pull-out height. This may limit the operational role of the aircraft._

This doesn't seem like an aircraft that can set a certain RPM and stop accelerating straight down.


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## FLYBOYJ (May 28, 2014)

Greyman said:


> I don't think that's how it works, but my knowledge of engines and propellers isn't the greatest so I'll leave it to the more knowledgeable folks.


I've been flying for 20 years and am also a flight instructor. I've been working in the aviation business for 35 years. I think I know a little something about this stuff! 


Greyman said:


> Interestingly, with regards to the pilot's notes, the Barracuda I, II (Merlin 30 32) are as you describe, but the Barracuda II III (Merlin 32) notes give no mention of RPM, but say the dive should be entered with not less than +6lb./sq.in. boost to avoid gaining excess speed.


 And boost and RPM are used in conjunction with each other when flying a high performance aircraft with a constant speed propeller.


Greyman said:


> This indicates to me that the reason for the 2,000 rpm is due to a propeller damage/overspeeding issue: the smaller pitch range on the 3-bladed prop compared to the 4-bladed, 32 degree prop.


 No it indicates that you are not going to over speed the engine or over boost it. You are also keeping the propeller at a pitch that will limit efficiency, slowing the aircraft down and preventing you from reaching Vne at a given dive altitude.


Greyman said:


> All this aside - in reading A&AEE dive bombing tests with the Barracuda II (merlin 32) the aircraft could be dived to 300 IAS with brakes deployed, 2000 rpm and 0lb boost.
> 
> A telling bit in the 'conclusions' of the report:
> 
> ...


No, but this is the technique developed to dive the aircraft at speeds that won't wreck the engine or airframe when diving from 5000'.

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## Greyman (May 28, 2014)

I still have issues with some of what you're saying - but overall it doesn't matter as it appears I was misreading you.

I thought you were saying that setting an aircraft's prop speed to 'X' would stop it from accelerating past a certain speed in a vertical dive.


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## stan reid (May 28, 2014)

I believe the ultimate dive bomber, the Japanese Ohka, had a maximum dive speed of around 650 mph.


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## FLYBOYJ (May 28, 2014)

Greyman said:


> I still have issues with some of what you're saying - but overall it doesn't matter as it appears I was misreading you.
> 
> I thought you were saying that setting an aircraft's prop speed to 'X' *would stop it from accelerating past a certain speed in a vertical dive*.



It would to a point at a certain altitude because the propeller is not operating at it max efficiency. 5000' is mentioned in this discussion. I think it's obvious if you dive a barracuda from 30,000' and keep the prop in low pitch, it's lack of efficiency will be overcome by mother gravity.


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## RCAFson (May 28, 2014)

Greyman said:


> I don't think that's how it works, but my knowledge of engines and propellers isn't the greatest so I'll leave it to the more knowledgeable folks.
> 
> Interestingly, with regards to the pilot's notes, the Barracuda I, II (Merlin 30 32) are as you describe, but the Barracuda II III (Merlin 32) notes give no mention of RPM, but say the dive should be entered with not less than +6lb./sq.in. boost to avoid gaining excess speed.
> 
> ...



Do you know the aircraft weight and bomb load for that test?

Here's the exact wording of the paragraph from the Feb 1945 Pilot's Notes:



> 49. Diving
> 
> (i) The dive should be entered smoothly at not less than +6 Lb./sq.in. boost. This will avoid any tendency for the carburettor to cut momentarily due to the effect of negative g. The throttle lever may be retracted during the dive to avoid gaining excessive speed.


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## GrauGeist (May 28, 2014)

stan reid said:


> I believe the ultimate dive bomber, the Japanese Ohka, had a maximum dive speed of around 650 mph.


The MXY7 may have had a high speed in it's final dive, but even then, it had terrible accuracy.

And technically speaking, the Ohka wasn't a "dive bomber" but rather a flying bomb...


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## Greyman (May 28, 2014)

RCAFson said:


> Do you know the aircraft weight and bomb load for that test?
> 
> Here's the exact wording of the paragraph from the Feb 1945 Pilot's Notes:



Good catch on the Pilot's Notes, different meaning if read correctly.

Condition of the Barracuda during the dive was 13,900 lb, 4x 500 lb GP bombs loaded.



FLYBOYJ said:


> It would to a point at a certain altitude because the propeller is not operating at it max efficiency. 5000' is mentioned in this discussion. I think it's obvious if you dive a barracuda from 30,000' and keep the prop in low pitch, it's lack of efficiency will be overcome by mother gravity.



That I'm prepared to believe. It was the image of a Barracuda diving straight down--not accelerating--at 260 IAS that had my eyebrow raised.


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## FLYBOYJ (May 28, 2014)

Greyman said:


> That I'm prepared to believe. It was the image of a Barracuda diving straight down--not accelerating--at 260 IAS that had my eyebrow raised.



The picture is reality if started from 5000' as the pilot's notes say.


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## Greyman (May 28, 2014)

No, the 5000 foot figure is mentioned (in the A&AEE conclusions) because beyond that, the Barracuda will _exceed _the limiting dive speed, not stop accelerating and coast down at 260 IAS.


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## FLYBOYJ (May 28, 2014)

Greyman said:


> No, the 5000 foot figure is mentioned (in the A&AEE conclusions) because beyond that, the Barracuda will *exceed *the limiting dive speed, not stop accelerating and coast down at 260 IAS.


Exactly but it's also mentioned in the pilot's notes for the same reason, remember you're looking at "a picture." The numbers paint something a bit different.


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## stona (May 29, 2014)

RCAFson said:


> Can you name any dive bomber attack on a carrier that was stopped by AA? NO WW2 AA system had the capability to defeat a determined DB attack, even with considerably larger numbers of defending ships than were present when Illustrious was attacked.



RN carriers survived air attacks in the Mediterranean. It really depends how you qualify 'determined'.

In operations off Crete the light cruiser HMS Fiji survived thirteen hours of more or less continuous air attack before finally sustaining two hits which proved fatal. This may have been due to the fact that she had run out of ammunition and was reduced to firing practice (solid) shot at the incoming aircraft before ceasing fire altogether. Ordinary Seaman Leonard Michaels, a survivor, said with typical understatement that his 'emboldened the attacking aircraft.' 

HMS Kipling was attacked 83 times in roughly five hours but survived. HMS Kandahar survived 22 attacks in four hours and forty five minutes but survived. Not carriers and obviously smaller and harder to hit, but they survived what I would call determined attack.

Cheers

Steve


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## Juha (May 29, 2014)

There are several cases of ships surviving when attacked by numerous DBs, one happened on June 5 1942 during the Battle of Midway. 58 SBDs from Enterprise and Hornet attacked lonely DD Tanikaze which zigzagged furiously and fired "a large volume of small caliber and anti-aircraft fire." She suffered damage, bomb fragments from near-misses caused explosion in after turret (6 KIA) but shot down one of Enterprise's SBDs (2 KIA). She survived most probably because of skillfull manoeuvring but probably partly because of that "a large volume of small caliber and anti-aircraft fire."


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## RCAFson (May 29, 2014)

stona said:


> RN carriers survived air attacks in the Mediterranean. It really depends how you qualify 'determined'.
> 
> In operations off Crete the light cruiser HMS Fiji survived thirteen hours of more or less continuous air attack before finally sustaining two hits which proved fatal. This may have been due to the fact that she had run out of ammunition and was reduced to firing practice (solid) shot at the incoming aircraft before ceasing fire altogether. Ordinary Seaman Leonard Michaels, a survivor, said with typical understatement that his 'emboldened the attacking aircraft.'
> 
> ...



IOW, there are no (AFAIK) examples of carriers defeating DB attacks with AA. Certainly, there are lots of examples of ships evading being hit by manoeuvre or because the bombs simply missed as did the vast majority of those aimed at Illustrious. Fliegerkorps X had been formed with the specific intention of sinking an RN carrier with heavy AP bombs. In their initial attack on Illustrious they achieved a measure of surprise but subsequent attacks were much less successful.


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## stona (May 29, 2014)

Actually the attack on Illustrious was disrupted by the FAA's Fulmars. The final attacking formation was intercepted and only one Ju 87 of this group achieved a hit. This bomb struck about 6 metres forward of the after lift and penetrated to the hangar deck before exploding on the ammunition lift. Most of the Ju87s, but not all, were dropping 500Kg armour piercing bombs with delay fuses. Some accounts say that the second and third attacks dropped 1000Kg bombs. I don't recall what delay the Germans had decided on for shipping attacks of this type. The British varied between 0.1 and 0.3 seconds depending on the weight of the bomb and altitude from which it was dropped.

Illustrious sustained six direct hits and several near misses in less than seven minutes. The attack was brilliantly executed by 40 Ju 87s commanded by experienced men who knew exactly how to go about dividing and defeating the fleets anti aircraft defences.

A subsequent attack (around 16.00) by 15 Ju 87s escorted by Bf 110s was foiled not because the British had ample warning but because the FAA Fulmars were in a position to disrupt it as the fortuitously returned, refuelled and rearmed, from Malta at the right time. Luck plays a part in war as in everything else. One further hit was sustained, tragically exploding on the hangar deck where a temporary sick bay had been rigged, killing 30 men instantly. Bad luck has a role too.

As for surprise Cunningham knew that the Luftwaffe was present on Sicilian airfields as evidenced by intelligence reports of 9th January, the day before the attack. The Luftwaffe was brilliant at rapid redeployments and Fligerkorps X had 96 Ju 87s ready for action (from Comiso and Catania) on the 8th January, just three days after their deployment.
He also had roughly one hours warning of an impending _German_ attack from intercepted Luftwaffe radio traffic. What neither he, nor his intelligence officer, knew was just how professional and ferocious this attack would be, particularly compared to the somewhat half hearted efforts of the Italians. In this aspect Cunningham, Boyd and the rest of the RN were taken completely by surprise.

Cheers

Steve


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## RCAFson (May 29, 2014)

Cunningham also had to expect that the Luftwaffe would attack the convoy that he was escorting through to Malta.


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## ohogain (Jun 8, 2014)

Which dive bombers were vertical dive bombers and which ones weren't?

From reading above, the Stuka and the Helldivers were vertical dive bombers. What about Henschel Hs 123? Heinkel He 50? Heinkel He 66/Aichi D1A? etc.


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## Wildcat (Jun 11, 2014)

A-31 Vengeance was.


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## Shortround6 (Jun 11, 2014)

There may be a bit of confusion (or not?) as in the plane may be pointed straight down ( axis of plane is 90 degrees to surface of the earth) but the flight path may not be 90 degrees. The wings are still trying to provide "lift" or a force 90 degrees (or close) to the axis of the plane which would force the actual flight path "forward" (as in the direction of the canopy?). 

Once you get around 80 degrees it gets rather academic or good for winning bar bets. A 80.54 degree dive will have the plane dropping 6 feet for every 1 foot of forward travel. a 59.97 degree dive drops 1.73 feet for every foot of forward travel and a 45 degree dive is 1 foot fot 1 foot. Even a 10 foot drop for each foot of forward travel is still only an 84.29 degree dive.


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## BiffF15 (Jun 11, 2014)

Shortround6,

Your understanding of dive angles is good. Remember, that the aircraft can be "trimmed" to an airspeed, and if the speed in a pure vertical dive (90') is held constant the aircraft will go "straight" down. However, in WW2 they didn't have a Heads Up Display to help them determine straight down. However, they did the math and figured out that if you are steep (greater dive angle than planned), fast (higher airspeed than planned) and press below your pickle altitude then your accuracy goes up. The pure vertical dive removes / reduces the dive angle variable from the equation.

Cheers,
Biff


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## GrauGeist (Jun 11, 2014)

Biff, not sure about other dive bombers, but the Ju87 had an incline indicator etched into the port side of the canopy that gave the pilot a dive angle at a glance.

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## cherry blossom (Jul 15, 2014)

I found something interesting in Manfred Griehl's “Junkers Ju 87 Stuka” (English translation published by Airlife 2001) on pages 46-7 discussing the tests on the V4 as reported in January 1937:

“In nearly vertical dives from 3,500 metres to 1000 metres, the dive brakes led to a stable terminal speed of 450 kph.”

This is much slower than I had imagined. However, clearly increasing the weight will increase the terminal speed. Some of the tests were stated to have used full tanks and a SC 250 bomb (for example establishing the take off distance) but there is nothing written about the weight during the dives. If we imagine that a loaded 1942 Ju 87 D5 had double the weight and identical drag, should we expect a terminal speed of 635 kph?
ps. Looking more closely at my latest purchase, I see that page 61 states that the dive brakes held the B version to between 500 and 600 kph and that page 93 states that the D-5 was tested up to 650 kph in dives at Rechlin.

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## Denniss (Jul 15, 2014)

The production D-5 should have discarded the dive brakes as they weren't used as dive bombers anymore.

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## Barrett (Dec 14, 2017)

SBD's dived at about 240 kts usually at 70 degrees. I got to know Dick Best well, and his discussions were clinically precise. He said "I liked to dive from the bow because it forced me to get steep." However, comma, he pinwheeled Akagi from broad on the port beam.


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