View source for Martin P4M Mercator

{{Short description|WW2-era American maritime reconnaissance aircraft}}
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{{Infobox aircraft
 |name= P4M Mercator
 |image= P4M-1 Mercator in flight.jpg
 |caption= United States Navy P4M-1
 |type= Patrol bomber
 |national_origin = [[United States]]
 |manufacturer= [[Glenn L. Martin Company|Martin]]
 |designer=
 |first_flight= 20 October 1946
 |introduction= [[1950 in aviation|1950]]
 |retired= [[1960 in aviation|1960]]
 |status= Retired
 |primary_user= [[United States Navy]]
 |more_users=
 |produced=
 |number_built= 21
 |variants=
}}

The '''Martin P4M Mercator''' was a maritime reconnaissance aircraft built by the [[Glenn L. Martin Company]]. The Mercator was an unsuccessful contender for a [[United States Navy]] requirement for a long-range maritime patrol bomber, with the [[Lockheed P-2 Neptune|Lockheed P2V Neptune]] chosen instead. It saw a limited life as a long-range electronic [[reconnaissance]] aircraft. Its most unusual feature was that it was powered by a combination of [[piston engine]]s and [[turbojet]]s, the latter being in the rear of the engine nacelles.

==Design and development==
Work began on the Model 219 in 1944, as a replacement for the [[Consolidated PB4Y Privateer|PB4Y Privateer]] long-range patrol bomber, optimised for long range minelaying missions, with the first flight being on 20 October 1946.<ref name="WoF p139">Lake and Dorr 2000, p.139.</ref> A large and complicated aircraft, it was powered by two [[Pratt & Whitney]] [[Pratt & Whitney Wasp Major|R4360 Wasp Major]] 28-cylinder [[radial engine]]s. To give a boost during takeoff and combat, two [[Allison J33]] turbojets were fitted in the rear of the two enlarged engine nacelles, the intakes being beneath and behind the radial engines.<ref name="WoF p138-9">Lake and Dorr 2000, pp. 138–139.</ref> The jets, like those on most other piston/jet hybrids, burned gasoline instead of jet fuel which eliminated the need for separate fuel tanks.

A [[tricycle undercarriage]] was fitted, with the nosewheel retracting forwards. The single-wheel main legs retracted into coverless fairings in the wings, so that the sides of the wheels could be seen even when retracted. The wings themselves, unusually, had a different airfoil cross-section on the inner wings than the outer.

Heavy defensive armament was fitted, with two 20&nbsp;mm (.79&nbsp;in) cannon in an Emerson nose turret and a Martin tail turret, and two 0.5&nbsp;in (12.7&nbsp;mm) machine guns in a Martin dorsal turret. The bomb bay was, like British practice, long and shallow rather than the short and deep bay popular in American bombers. This gave greater flexibility in payload, including long torpedoes, bombs, mines, depth charges or extended-range fuel tanks.<ref name="Ferret 216-7">Dorr and Burgess 1993, pp. 216–217.</ref>

==Operational history==
[[File:Martin P4M-1 Mercator of VP-21 in flight in the early 1950s (NH 101801-KN).jpg|thumb|right|P4M-1 of [[VP-21 (1943-69)|VP-21]]]]
The US Navy chose the smaller, simpler, cheaper and better performing P2V Neptune for the maritime patrol requirement, but nineteen aircraft were ordered in 1947 for high-speed minelaying purposes. The P4M entered service with [[VP-21 (1943-69)|Patrol Squadron 21 (VP-21)]] in 1950, the squadron deploying to [[NAS Port Lyautey]] in [[French protectorate of Morocco|French Morocco]].<ref name="Ferret p217">Dorr and Burgess 1993, p.217.</ref> It remained in use with VP-21 until February 1953.<ref name="DANAS v2 p125">Roberts 2000, p.125.</ref>

From 1951, the 18 surviving production P4Ms were modified for the electronic reconnaissance (or [[SIGINT]], for ''signals intelligence'') mission as the '''P4M-1Q''', to replace the [[PB4Y-2 Privateer]]. The crew was increased to 14 and later 16 to operate all the surveillance gear, and the aircraft was fitted with a large number of different antennae.<ref name="WoF p141-2">Lake and Dorr 2000, pp. 141–142.</ref>

[[File:Martin P4M Mercator VQ-2 06.09.56.jpg|thumb|right|P4M-1Q Mercator of VQ-2 electronics reconnaissance squadron in September 1956 - note extra radar 'bulges' on this variant]]

Starting in October 1951, electronic surveillance missions were flown from [[U.S. Naval Station Sangley Point]] in the [[Philippines]], later from [[Naval Air Station Iwakuni]], [[Japan]], and [[Naval Air Station Atsugi]], Japan, by a secretive unit that eventually gained the designation [[VQ-1|Fleet Air Reconnaissance Squadron One (VQ-1)]]. Long missions were flown along the coast (about {{cvt|30|nmi|km|disp=or}} offshore) of Vietnam, China, North Korea and the eastern Soviet Union, and were of a highly secret nature; the aircraft sometimes masqueraded as regular P2V Neptunes in radio communications, and often flew with false [[United States military aircraft serials#United States Navy and Marine Corps|serial numbers]] (Bureau Numbers) painted under the tail. Operational missions were always flown at night, during the dark with the moon when possible, and with no external running lights.<ref name="Ferret p217,220">Dorr and Burgess 1993, pp. 217, 220.</ref>

The Mercators were replaced by the [[A-3 Skywarrior|EA-3B Skywarrior]], which, being carrier-based, had a greater degree of flexibility, and the larger [[EC-121 Warning Star|Lockheed WV-2Q Warning Star]]. Final withdrawal from service was in 1960 after which all of the remaining P4Ms were scrapped.<ref name="Ferret p222">Dorr and Burgess 1993, p.222.</ref>

==Losses==
* On 8 March 1951 a Mercator flew into the [[Atlantic Ocean]] off [[Florida]], killing four of its crew.<ref>[http://cgibin.rcn.com/jeremy.k/cgi-bin/gzNavySearch.pl?target=Mercator&series=3 J. Baugher listing]</ref>
* On 6 February 1952, a Mercator [[Water landing|ditched]] in the [[Aegean Sea]] north of [[Cyprus]] at night, out of fuel, with no power, losing only the aircraft commander/pilot after the crew was in the water. The crew was rescued by the [[Royal Navy]] [[destroyer]] {{HMS|Chevron}}.<ref>{{cite magazine |last= |first= |date= March–April 1997 |title= |url= |magazine=Naval History |location= |publisher=[[United States Naval Institute]] |access-date=}}</ref><ref>The aircraft were also operated from [[Morocco]] by [[VQ-2|Fleet Air Reconnaissance Squadron 2 (VQ-2)]]. One garbled version of this incident provided by a former U.S. Navy seaman who served in the Mediterranean is that this aircraft was intercepted near [[Soviet Union|Soviet]] airspace off the [[Ukrainian Soviet Socialist Republic]] and shot down, crashing into the [[Mediterranean Sea]] with the loss of all crew.</ref>
* On 22 August 1956, a Mercator was shot down near Shanghai by Chinese fighters of the [[2nd Aviation Division (People's Republic of China)|2nd Aviation Division]],<ref>{{cite web |url = http://www.plaaf.net/Air-Force-Deploy/Guangzhou-Military-Region-Deploym/201004/667.html |title = 空2师(歼击航空兵) |website = 中国空军网 |date = 2012-03-19 |access-date = 2014-11-04 |archive-url= https://web.archive.org/web/20141023034654/http://www.plaaf.net/Air-Force-Deploy/Guangzhou-Military-Region-Deploym/201004/667.html |archive-date = 2014-10-23 }}</ref> with its crew of 16 all killed.<ref name="Ferret p220-1">Dorr and Burgess 1993, pp. 220–221.</ref>
* On 19 November 1957, a Mercator was lost in an accident.<ref>[http://cgibin.rcn.com/jeremy.k/cgi-bin/gzNavySearch.pl?target=Mercator&series=3 J. Baugher listing]</ref>
* On 6 January 1958,<ref>{{Cite web|url=http://www.joebaugher.com/navy_serials/thirdseries13.html|title=US Navy and US Marine Corps BuNos--Third Series (120341 to 126256)}}</ref> a P4M-1Q of JQ-3<ref>{{Cite web |url=http://www.portlyautey.com/ECM-2.htm |title=In Memoriam of VQ-2 Shipmates Lost|access-date=2024-09-07 |archive-url=https://web.archive.org/web/20160104153422/http://www.portlyautey.com/ECM-2.htm |archive-date=2016-01-04 |url-status=dead }}</ref> [[List of accidents and incidents involving military aircraft (1955–1959)#1958|crashed]] at [[Ocean View, Virginia|Ocean View]], Virginia,  when it lost an engine on approach to [[NAS Norfolk]], Virginia, killing four crew and injuring three civilians.<ref>Associated Press, "Four Missing In Air Crash", ''The Anderson Independent'', Anderson, South Carolina, Tuesday 7 January 1958, Volume 41, Number 99, page 1.</ref>
* On 16 June 1959, a P4M-1Q was attacked by two North Korean [[MiG-17]]s with heavy damage and serious injury to the tail gunner.<ref name="Ferret p221-2">Dorr and Burgess 1993, pp. 221–222.</ref>
* On 19 January 1960, a [[VQ-2|Fleet Air Reconnaissance Squadron 2 (VQ-2)]] P4M-1Q JQ-16 (BuNo 124365) crashed en route to [[Adana Air Base]] in [[Turkey]], killing all 16 aircrew. The [[Royal Air Force]] Mountain Rescue Team based at [[Nicosia]], Cyprus, recovered the bodies of 12 crew members before being forced to leave the recovery of the remaining bodies and body parts until the spring.

==Variants==
;XP4M-1
:Two prototype aircraft with two R-4360-4 engines.
;P4M-1
:Production aircraft with two R-4360-20A engines, 19 built.
;P4M-1Q
:P4M-1s redesignated when modified for radar countermeasures.

==Operators==
;{{USA}}
* [[United States Navy]]

==Specifications (P4M-1 Mercator)==
[[File:Martin P4M-1Q Mercator 3-view line drawing.png|frameless|right|3-view line drawing of the Martin P4M-1Q Mercator]]

{{Aircraft specs
|ref=United States Navy aircraft since 1911,<ref name="Swanborough">{{cite book |last1=Swanborough |first1=Gordon |last2=Bowers |first2=Peter M. |title=United States Navy aircraft since 1911 |date=1976 |publisher=Naval Institute Press |location=Annapolis |isbn=0870217925 |page=513 |edition= 2nd}}</ref> Naval Fighters #37: Martin P4M-1/-1Q Mercator<ref name=Ginter>{{cite book |last1=Ginter |first1=Steve |title=Martin P4M-1/-1Q Mercator |date=December 1996 |publisher=S. Ginter |location=California |isbn=0-942612-37-X}}</ref>
|prime units?=imp
<!--
        General characteristics
-->
|crew=9 (patrol bomber); 16 (Electronic reconnaissance)
|capacity=
|length ft=86
|length in=2.5
|length note=
|span ft=114
|span in=0+1/16
|span note=
|height ft=29
|height in=2+1/16
|height note=
|wing area sqft=1311
|wing area note=
|swept area sqft=<!-- swing-wings -->
|swept area note=
|volume ft3=<!-- lighter-than-air -->
|volume note=
|aspect ratio=9.87
|airfoil=root: [[NACA airfoil|NACA 2417]] (17%); tip: [[NACA airfoil|NACA 2412]] (12%)
|empty weight lb=48536
|empty weight note=
|gross weight lb=83378
|gross weight note=
|max takeoff weight lb=
|max takeoff weight note=
|fuel capacity=<br />
:::'''Fuel ([[115/145 Avgas]]):''' {{cvt|3500|USgal|impgal l}} total in 4 wing tanks and 4 auxiliary tanks in the bomb bay
:::'''Oil:''' {{cvt|216|USgal|impgal l}} in 2 nacelle tanks
:::'''Water''' {{cvt|9|USgal|impgal l}} in 2 nacelle tanks

|more general=
<!--
        Powerplant
-->
|eng1 number=2
|eng1 name=[[Pratt & Whitney R-4360-20A Wasp Major]]
|eng1 type=28-cylinder air-cooled radial piston engines
|eng1 hp=3250
|eng1 note=with water injection
:::('''XP4M-1:''' {{cvt|2975|hp}} R-4360-4)
|power original=
|thrust original=

|eng2 number=2
|eng2 name=[[Allison J33-A-10A]]
|eng2 type=[[turbojet engine]]s
|eng2 hp=<!-- prop engines -->
|eng2 shp=<!-- prop engines -->
|eng2 lbf=4600
|eng2 note=<br />
:::('''XP4M-1:''' {{cvt|3825|lbf}} J33-A-17)
|eng2 lbf-ab=<!-- afterburners -->

|prop blade number=4
|prop name=[[Hamilton Standard]]
|prop dia ft=15
|prop dia in=2
|prop dia note=reversible-pitch constant-speed propellers
<!--
        Performance
-->
|max speed mph=410
|max speed note= at {{cvt|20100|ft}}
|max speed mach=<!-- supersonic aircraft -->
|cruise speed mph=
|cruise speed note=
|stall speed mph=
|stall speed note=
|never exceed speed mph=
|never exceed speed note=
|minimum control speed mph=
|minimum control speed note=
|range miles=2840
|range note=
|combat range miles=
|combat range note=
|ferry range miles=4230
|ferry range note=with bomb-bay auxiliary tanks fitted
|endurance=<!-- if range unknown -->
|ceiling ft=34600
|ceiling note=
|g limits=<!-- aerobatic -->
|roll rate=<!-- aerobatic -->
|glide ratio=<!-- sailplanes -->
|climb rate ftmin=
|climb rate note=
|time to altitude=
|sink rate ftmin=<!-- sailplanes -->
|sink rate note=
|lift to drag=
|wing loading lb/sqft=
|wing loading note=
|fuel consumption lb/mi=
|power/mass=
|thrust/weight=

|more performance=
<!--
        Armament
-->
|armament=
* 4 × {{cvt|20|mm|3}} cannon in nose and tail turrets
* 2 × {{cvt|0.50|in|2}} machine guns in dorsal turret
* Up to {{cvt|12000|lb}} of bombs, mines, depth charges, or torpedoes
|avionics=* [[AN/APS-33]] search radar
}}

==See also==
{{aircontent
|similar aircraft=
* [[Avro Shackleton]]
* [[Consolidated PB4Y-2 Privateer]]
* [[Lockheed P-2 Neptune]]
* [[Lockheed P-3 Orion]]
|lists=
* [[List of United States Navy aircraft designations (pre-1962)]]
}}

==References==
{{reflist}}
* Dorr, Robert F. and Richard R. Burgess. "Ferreting Mercators". ''[[Air International]]'', October 1993, Vol.45, No. 4. ISSN 0306-5634. pp.&nbsp;215–222.
* Lake, Jon and Robert F. Dorr. "Martin P4M Mercator". ''Wings of Fame''. Volume 19. London:Aerospace Publishing, 2000. {{ISBN|1-86184-049-7}}. pp.&nbsp;138–149.
* Roberts, Michael D. ''[https://web.archive.org/web/20080915133000/http://www.history.navy.mil/branches/dictvol2.htm Dictionary of American Naval Aviation Squadrons:Volume 2: The History of VP, VPB, VP(HL) and VP(AM) Squadrons]''. Washington, DC:Naval Historical Center, 2000.

==External links==
{{Commons category-inline}}

{{Martin aircraft}}
{{USN patrol aircraft}}
{{Authority control}}

[[Category:Aircraft with auxiliary jet engines]]
[[Category:1940s United States patrol aircraft|Martin PM4 Mercator]]
[[Category:Martin aircraft|P4M]]
[[Category:Aircraft first flown in 1946]]
[[Category:Shoulder-wing aircraft]]
[[Category:Twin piston-engined tractor aircraft]]
[[Category:Twinjets]]
[[Category:Aircraft with retractable tricycle landing gear]]