AN/APS-13 - total weight of this tail warning radar?

[Starly]

I've been trying to find a credible source that mentions weight of this radar system. Specifically on P-51D. Somebody mentioned on this forum that one pilot said it added extra 400 lbs of weight to the tail, but I was only able to find info that overall weight was only 25 lbs. Does anyone have any info on this? Preferably something official or report from a WW2 technician.

TL;DR AN/APS-13 was a tail warning radar used on some WW2 planes. It started beeping when there was something behind the plane.

Edit: Tail warning radar on P-51 ?
This is the post where the weight of 400 lbs was mentioned. It was from Bill Dunn's book.

 

[Wurger]

In the same thread ..

Tail warning radar on P-51 ?

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.

ww2aircraft.net

The full copy of the excerption in the post with the link above ...

S E C R E T: TRIALS OF A.N.A.P.S. 13 AS A RANGE INDICATOR
F.I.U. Report No. 254.

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

the source: AN/APS-13 Tail Warning Radar

 

[SaparotRob]

Hi Starly, welcome. Great question.

 

[Starly]

In the same thread ..

Tail warning radar on P-51 ?

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.

ww2aircraft.net

The full copy of the excerption in the post with the link above ...

S E C R E T: TRIALS OF A.N.A.P.S. 13 AS A RANGE INDICATOR
F.I.U. Report No. 254.

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

the source: AN/APS-13 Tail Warning Radar

Yes I noticed that a while later.
I'll keep this post up though. So others will have easier time finding this information and they won't have to dig as deep to find it.

Thanks!

 

[ThomasP]

"AP 2891G Vol. 1, 2nd Ed. AN/APS-13 / Monica Mk. 7 (ARI.5664)" from 1948 lists the total weight of the "main units" of equipment as 21 lbs.

Items listed under "main units":

RT-34/APS-13 transmitter-receiver
MT49/APS-13 mounting base for transmitter-receiver
AS62/APS-13 Aerial System
C76/APS-13 control box
ID42/APS-13 indicator light
Warning Bell
Connector Set

Sorry, I cannot post the manual due to copyright.

 

[MIflyer]

Here is a photo, and the schematic as well. It is about the size of a microwave oven.

 

[cvairwerks]

From AN 08-30APS13-2, the installed weight should be around 34 pounds, plus whatever the additional structure installation adds. A quick run thru the drawings, I'd guesstimate about 5 pounds for the angles, plates and doublers and the associated hardware for the install.

 

[GreenKnight121]

So... 40 lbs, not 400.

Perhaps the author's source said "40.0 lb" and he missed the period.