# Tail warning radar on P-51 ?



## Park (Dec 15, 2013)

I read about tail warning radar in Fight Journal on page 34, I was not aware of this, anyone ever heard of this ?

Ken


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## fubar57 (Dec 15, 2013)

Someone just posted something about this very recently. I'll see if I can find the post.

Geo


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## fubar57 (Dec 15, 2013)

From "Pilot Training Manual for the Mustang P-51"







From this site....http://www.ww2aircraft.net/forum/start-finish-builds/geedees-p-51d-cockpit-project-18113-34.html Starting from Post #498

Geo


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## Airframes (Dec 15, 2013)

Have a look at Geedee's thread on his 1:1 P-51 cockpit, in the modelling section, and you'll see the warning bell, and a drawing of the antenna, which was mounted near the top of the fin. Off hand, I can't remember the dates, but it came into service in the ETO either in very late 1944, or early 1945, and was, of course, in service from then, until war's end, in the PTO.
This was a fairly basic piece of equipment, which warned of the presence of an aircraft directly to the rear, with a relatively narrow arc each side of the center line, and did not distinguish between friend or foe. Also, at lower altitudes ( I think below around 4,000 feet), the effects of 'ground return' could activate the radar, setting off the alarm bell.


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## drgondog (Dec 15, 2013)

I know that the last block P-51D-20/-25NA and corresponding P-51K's had the AN/APS-13 tail warning radar. Positioned on top 1/3 of the vertical stab in front of rudder.


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## Airframes (Dec 15, 2013)

Not a very good photo, but this is what the fin-mounted antenna looked like. I've got a better pic somewhere, but a bit short on time at the moment.

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## glennasher (Dec 15, 2013)

According to Bill Dunn's book, he hated the thing. He claimed it added 400 lbs. to the tail of the aircraft and didn't provide enough benefit to justify the weight addition, not to mention COG. etc.


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## pattle (Dec 15, 2013)

Was it a success? it sort of makes me think of the parking sensors on my car which can at times be a pain rather than a benefit.


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## Park (Dec 15, 2013)

Well I'll be darn, Like many on the forum I've been reading about WWII aircraft for over 40 years and never heard of this...learn something every day !


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## bobbysocks (Dec 15, 2013)

pattle said:


> Was it a success? it sort of makes me think of the parking sensors on my car which can at times be a pain rather than a benefit.



from the conversations i have had...they couldnt use it while flying formation...except for maybe tail end charlie. when they spotted the enemy...dropped their tanks...turned on guns...etc..they forgot to turn that on. if they did turn it on...everytime a plane past through the cone the bell would go off and a lot just found it too distracting. they relied more on the mirrors and their wing man.


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## pattle (Dec 16, 2013)

bobbysocks said:


> from the conversations i have had...they couldnt use it while flying formation...except for maybe tail end charlie. when they spotted the enemy...dropped their tanks...turned on guns...etc..they forgot to turn that on. if they did turn it on...everytime a plane past through the cone the bell would go off and a lot just found it too distracting. they relied more on the mirrors and their wing man.



Distracting, a bit like the parking sensors on my car then! Some Lancasters carried a tail warning and gun laying system called Village Inn which took the shape of a pointed dome and poked out from the rear fuselage. I think the P51 radar to be more like Monica which was also used by Bomber Command and which was abandoned after it was discovered that German night fighters were attracted to its beams.


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## Mike Williams (Dec 16, 2013)




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## Airframes (Dec 16, 2013)

Village Inn wasn't so much a tail warning radar, as in 'Boozer' or 'Monica', but a gun laying system (AGLT) for the rear turret, using radio/radar and infra red. The twin lamps in the nose blister of later Lancs were infra red emitting, and intended as identification of a 'friendly' aircraft to the AGLT, to prevent the rear gunner locking on and opening fire.


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## pbehn (Dec 17, 2013)

glennasher said:


> According to Bill Dunn's book, he hated the thing. He claimed it added *400 *lbs. to the tail of the aircraft and didn't provide enough benefit to justify the weight addition, not to mention COG. etc.



Surely a typo?


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## FLYBOYJ (Dec 17, 2013)

glennasher said:


> According to Bill Dunn's book, he hated the thing. He claimed it added 400 lbs. to the tail of the aircraft and didn't provide enough benefit to justify the weight addition, not to mention COG. etc.





pbehn said:


> Surely a typo?



It has to be or Mr. Dunn was very wrong (no disrespect) According this link the APS-13 (British ANAPS-13) weighed 20 pounds and was installed on the Tempest as well.

The Hawker Tempest Page


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## drgondog (Dec 17, 2013)

glennasher said:


> According to Bill Dunn's book, he hated the thing. He claimed it added 400 lbs. to the tail of the aircraft and didn't provide enough benefit to justify the weight addition, not to mention COG. etc.



No way possible to add 400 pounds aft of the tail wheel and fly the airplane in a 51. The 85 gallons of fuel with a moment arm of a couple of feet made the 51 hoggish until the fuel burned down - just imagine a permanent 400 pound weight Anywhere from aft of the fuel tank to the tailwheel. It 'looks' like it weighs between 10-20 pounds max.

BTW Dunn's only possible exposure to the AN/APS-13 would have been with P-47D in 406FG. IIRC he wasn't flying much combat when he went to China after ETO duties complete.

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## glennasher (Dec 17, 2013)

He didn't like the aft fuel tank, either. Just going by what he wrote. I hadn't even heard of the tail-warning radar until then. 400 lbs. is what he claimed, I couldn't say how much it weighed, since I didn't know about it until reading the book.


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## Maxrobot1 (Dec 17, 2013)

The tail warning radar was used as an "off the shelf" item for fusing of the the Atomic bombs used on Japan. This was to ensure an air burst no matter what the barometric pressure was. 
Photos of the very early bombs show the radar antennae and replicas include them to varying degrees of accuracy.


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## pattle (Dec 17, 2013)

400lbs, that's 400 bags of sugar!


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## Airframes (Dec 17, 2013)

Sounds like a heck of weight, even if it included the wiring, actual 'black box', bell and switches etc, spread throughout the airframe from tail to cockpit. Maybe a total of 40 Pounds ?


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## pbehn (Dec 18, 2013)

How many gallons is 400Ibs of fuel ? When discussing the P51 with the rear tank full I have read many say it was tricky to fly, I never read about the additional weight of the radar though. It seems inconceivable they would put another 400 Ibs in the plane let alone in the back of it.


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## davparlr (Dec 18, 2013)

Although I can't prove it, I think the weight of the radar in the P-61 was about 400 lbs. I don't think they would ever put a gizmo that heavy in a fighter if it wasn't a sure thing.


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## FLYBOYJ (Dec 18, 2013)

pbehn said:


> How many gallons is 400Ibs of fuel ? When discussing the P51 with the rear tank full I have read many say it was tricky to fly, I never read about the additional weight of the radar though. It seems inconceivable they would put another 400 Ibs in the plane let alone in the back of it.



66.45 gallons. 1 gallon of avgas weighs 6.02 pounds.

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## stona (Dec 18, 2013)

pattle said:


> I think the P51 radar to be more like Monica which was also used by Bomber Command and which was abandoned after it was discovered that German night fighters were attracted to its beams.



The AN/APS-13 tail warning radar was the US version of Monica. It's a very similar thing. I'll try and find a weight, but it was definitely not 400 pounds.

I doubt that the P-51 manual would describe radar equipment weighing 400 pounds as 'light weight' 

This is the system.







Here's what is inside the unit.






This along with the panel in the cockpit is all you need. If the whole system weighed more than 20-30 pounds I'd be amazed.

Cheers

Steve

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## drgondog (Dec 18, 2013)

Maxrobot1 said:


> View attachment 250176
> The tail warning radar was used as an "off the shelf" item for fusing of the the Atomic bombs used on Japan. This was to ensure an air burst no matter what the barometric pressure was.
> Photos of the very early bombs show the radar antennae and replicas include them to varying degrees of accuracy.



According to other documentation - four were used with two required to validate the ~1300 AGL fuse height.


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## FLYBOYJ (Dec 18, 2013)

The link was posted earlier...

_"I. INTRODUCTION. 



1. Verbal instructions were received by Fighter Interception Unit from Air Defence Great Britain to carry out trials of A. N. A. P. S. 13 as a method of range finding in Tempest aircraft, operating against Flying Bombs at night. A Tempest V aircraft, fitted with the equipment, was delivered from Defford to the F. I. U. Tempest Detachment at R. A. F. Newchurch, for trials, at the end of July. 



II. DESCRIPTION OF EQUIPMENT 



2. The A. N. A. P. S. 13 consists of a Unit of approximately 15" by 8" by 10" overall dimensions, mounted on the port side of the aircraft behind the pilot. The pilot's control box is mounted on the starboard knock out panel and carries an on/off switch and a test switch for the indicator lamp, which is mounted near the gun sight. The indicator lamp will light up at a range, which is pre-set on the ground. A single dipole aerial is carried on the port wing near the wing tip. *The overall weight of the equipment is approximately 25 lbs. * 

III. NATURE OF TRIALS 



3. Since returning from Newchurch to Wittering for adjustment, the equipment has been flown six times by day and six times by night by the F. I. U. Tempest detachment. The day trials have been carried out on target aircraft, owing to the shortage of Divers when required; but all the night trials have been done with Divers as targets. 



IV. RESULTS OF TRIALS 



4. When the aircraft was delivered from Defford the range was pre-set at 800 yards and the light was permanently on at low levels. The aircraft was returned to Wittering where the range was set at 300 yards and the aircraft returned to Newchurch. 



5. During each of the twelve test flights the warning lamp came on at ranges of 300 to 350 yards, or when flying at less than 1500 feet above the ground. The light remains on to zero range. The dimming of the bulb is considered adequate. 



V. CONCLUSION 



6. As the equipment is small, and extremely easy to operate, it is ideal for Tempest aircraft. The present range setting is just within the firing range and should remain as it is. It gives no indication of closing speed, but this is not important, as the pilot can tell whether he is closing by the increase of the intensity of the flame from the propulsion unit of the bomb. 



VI. RECOMMENDATION 



7. The pilot's control panel and cabling is at present installed on the emergency jettison panel and in this position might cause difficulty in abandoning the aircraft. It is suggested that this unit be moved to a position on the same side of the fuselage above the petrol cocks. 



10th August 1944.
FIU/S. 505/ 16/ AIR Squadron Leader,
Commanding Fighter Interception Unit,
Royal Air Force, Wittering" _

http://www.hawkertempest.se/ElectronicWar.htm


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## stona (Dec 18, 2013)

25lbs, thanks for that.

I made a pretty good guess even if I say so myself 

Cheers

Steve


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## Airframes (Dec 18, 2013)

Good stuff Joe, and a good 'guesstimate' Steve.

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