Thursday, November 28, 2013

What? A Phantom for the US Army?


HISTORICAL BACKGROUND
Ever since the Key West Agreement of 1948 (pet name for the policy paper titled “Function of the Armed Forces and the Joint Chiefs of Staff”), which limited Army aviation activities to reconnaissance and medical evacuation purposes and put severe weight restrictions on any aircraft, the Army has maintained that the Air Force was too strategic (ie nuclear) minded and not giving enough attention to the tactical and logistical needs of the Army.  As a result the Army often pushed the envelope of the agreement limits, citing the need for better transport and close air support assets.

To try and smooth the troubled waters, in 1952 a memorandum of understanding was reached between USAF Secretary Thomas Finletter and US Army Secretary Frank Pace that removed all weight restrictions on helicopters operated by the Army.  It did however; place an arbitrary 5,000 pound weight restriction on any fixed-wing aircraft.

During the late 1950s the Army Aviation Test Board and the Aviation Combat Developments Agency (ACDA) began to jointly explore the feasibility of using Army-operated fixed-wing jet aircraft in the artillery adjustment, tactical reconnaissance, and ground attack roles.  In early 1958 three Cessna T-37As were borrowed from the Air Force for a one year evaluation program dubbed Project LONG ARM.  The Army’s evaluation found the T-37 to be ideal for their needs, and the Aviation Board and the ACDA recommended quantity procurement of the type.  But the Air Force, citing the Key West Agreement, put pressure on the Army and eventually the program was dropped. 

But the Army wasn’t done, the battle may have been won by the Air Force, but the war had just begun.  In 1961 the Army Aviation Test Board and the ACDA once again stirred the pot by trying not one, not two, but three jet aircraft types in a competitive “fly-off”.  The aircraft chosen were the Northrop N-156 lightweight fighter prototype, The Douglas A-4 Skyhawk, and the Fiat G.91.  Ostensibly these aircraft were to be used as tactical reconnaissance and target spotting and artillery adjustment roles, but it was hard not to notice that each of these aircraft had offensive weapons capability, which was clearly contrary to the Key West Agreement.  Again the Army’s tests were in vain because Air Force pressure again forced the Army to scuttle its plans for jet fixed-wing aircraft.

Meanwhile the Army had acquired a fleet of fixed-wing aircraft ranging from the Piper L-4 (730 pounds empty) to the DeHavilland-Canada U-1 Otter ( 4,431 pounds empty).  All of these aircraft easily fit under the limitations of the Pace-Finletter MOU of 1952.  Air Force apprehension rose when the Army in 1962 awarded a contract to DeHavilland- Canada  for the CV-2 Caribou (later the C-7).  This aircraft was exactly what the Army wanted, a rugged and reliable aircraft that could haul nearly 4 tons of cargo or 40 passengers into and out of the roughest forward air fields.  The Army quickly made it the poster child of Army Aviation.  Oh, did I forget to mention that it weighed 16,920 pounds empty?  Even though it was a tactical cargo aircraft, which was supposedly taboo, the Army  justified it by a new concept the Army was incorporating called “Air Mobility”.

By now you are wondering “what has all this got to do with the Phantom II?”  Be patient, I’m almost there.

Naturally the Air Force was a bit peeved.  The Army had not only purchased a tactical cargo aircraft, it had armed helicopters (which the Army was not supposed to do), and to add salt to the wound, the US Army talked the US Marine Corps into sponsoring a battlefield observation aircraft from Grumman, both sides knowing full well that the Navy would never buy it for the Marines.  But as a result the Army “found” this nice “little” Marine aircraft that nobody wanted and decided to be nice and order a bunch.  Enter the Grumman OV-1 Mohawk.  A bit heavy at around 11,500 pounds empty, but it was the perfect battlefield observation aircraft and it was really needed in a hot spot that was heating up called Vietnam.  It even had pylons which could carry fuel tanks (not to mention the odd gun pod or missile launcher). The Air Force was not amused.

Finally we get the Johnson-McConnell Agreement of 1966, where the Army agreed to turn over its fleet of Caribous and the newer Buffalo, and pursue their development of VTOL aircraft on a joint basis with the Air Force.  The Air Force agreed to let the Army continue to develop and operate rotary wing aircraft, without weight restrictions, and would not interfere with their tactical helicopter operations (even armed helicopters) in support of the Army’s mission.  The one aircraft that was an exception was the Mohawk which the Army was permitted to continue to use (It really was a great battlefield observation aircraft with its side looking radar and other sensors).

Sorry for the history lesson, but it is necessary to understand the climate that the McDonnell proposed Phantom II ground support aircraft for the Army was introduced into.

THE PROPOSED MCDONNELL PHANTOM II GROUND SUPPORT AIRCRAFT FOR THE ARMY
In 1961 McDonnell drew up specifications for two attack aircraft based on the F-4H airframe.  I don’t know if they ever were presented to the Army, but I assume they were because they are on the books as Models 98DA and 98DB with the US Army as the proposed customer.  This would have been about the time of the evaluation fly-off of the N-156, A-4, and the G.91, so I imagine that McDonnell didn't want to get left out if the Army was going for jet aircraft.

MODEL 98DA

The Model 98DA was a model F4H-1 modified for the Army ground support mission. It was offered in two versions - G-1 and alternate G-1 with changes as follows:
  1. Two place aircraft.
  2. Remove all electronic equipment items and replace with close support equipment to provide visual delivery of ground support weapons and visual lay down capabilities.
  3. Replace single main landing gear tire with dual 30 x 7.7 tires.
  4. Deactivate wing fold and remove catapult and arresting gear.
  5. Remove Sparrow III missiles and supporting equipment and electronics.
  6. Remove equipment refrigeration package for equipment cooling, utilizing cabin refrigeration unit to also cool equipment.
  7. Add cartridge starters and battery.
  8. Replace present arresting gear with lightweight hook.
  9. Add IFR boom receptacle.
  10. Powered by two General Electric J79-GE-8 turbojet or Allison AR-168-18 (Allison built Rolls Royce Spey RB-168) turbofan engines.
  11. (Alternate G-1 only) Add one M-61 Vulcan aircraft cannon with 930 rounds 20mm ammunition.
MODEL 98DB

The Model 98DB was the same as model 98DA but further modified for the Army ground support mission with changes as follows:
  1. Single-seat Aircraft
  2. Remove rear seat and all associated controls, instruments, and equipment. (Space available for equipment growth and/or reconnaissance capability)
  3. Remove rear canopy glass and replace with sheet metal.
  4. Remove rear canopy electrical and jettison equipment and modify manual controls to open and close hatch.
  5. Eliminate Central Air Data Computer (CADC) and flight control group equipment.
  6. Remove IFR Probe and all associated equipment.
  7. Remove variable bellmouth from engine duct, keep bellmouth controller to control variable inlet ramps.
  8. Powered by two General Electric J79-GE-8 turbojet engines.

THOUGHTS
It is evident that these proposed aircraft were clearly a much stripped-down attack version of the Phantom II.  Almost all of the air-to-air capability has been stripped away.  Some of the proposed changes indicate that this wasn’t intended to be a high-speed aircraft.  The dual main gear, obviously intended to help the aircraft operate out of rough, forward area airstrips, would have hung out into the airstream, and even if fairings would have been utilized to blend it into the wing, they would have had a performance hit.  The elimination of the CADC and bellmouth would also have curtailed any high-speed / altitude flight.  This aircraft was intended to be a mud-fighter – a low altitude, subsonic aircraft that could manually deliver an impressive load of munitions on a given target.

I am sure that the Army didn't show a lot of interest because, even in the stripped down state presented by these proposals, the F-4 was just too much of an aircraft both weight-wise and complexity to operate out of primitive forward area airstrips.  Maintenance would have been a head ache, and even with the dual main wheels, I am sure it would sink into any soft soil it would come in contact with.  The T-37, which was the early favorite, would have probably served the Army well in their intended role.  But in the end the Army didn't pursue any jet aircraft, and the Air Force won the war in the end.





REFERENCES:
  1. US Army Aircraft Since 1947, by Stephen Harding
  2. Note by the Secretaries to the Joint Chiefs of Staf- Functions of the Armed Forces and the Joint Chiefs of Staff – Reference J.C.S 1478 Series, dated 21 April 1948
  3. A History of Army Aviation: From Its Beginnings to the War on Terror, by James Williams
  4. Tactical Airlift. United States Air Force in Southeast Asia, by Ray Bowers
  5. McDonnell List of Proposed Models, dated 1 July 1974

REVISIONS:

28 November 2013 – Initial Post

Wednesday, November 20, 2013

Phantoms that never were built… RF-4M


In 1957 the British Secretary of State for Defense, Duncan Sands, presented a white paper which called for the elimination of manned aircraft in favor of missile systems.  To compound matters, the Royal Navy was chosen as the best means to deliver these missiles which would be submarine based ICBMs and tactical weapons delivered from their aircraft carriers.  This left the British Aircraft Industry and the Royal Air Force (RAF) with just one aircraft project on the books, a replacement for the venerable Canberra.  This resulted in the TSR2 project which, after spending 200 million pounds in development, was cancelled and the prototypes relegated to museums and the scrap yard.
The RAF needed a multi-purpose fighter, one which could perform the duties of the aging Hunter, Canberra, and Lightning aircraft currently in service.  The Royal Navy had already given up waiting for the V/STOL P.1154 which would not be available for 6 years (eventually itself cancelled), and had decided to move ahead with an Anglicized Phantom II to be known as the F-4K (or Phantom FG Mk.1).  The RAF needed an aircraft which would handle Interdiction, Ground Attack and Reconnaissance roles.  Since the Royal Navy had already chosen the Phantom, the RAF realized (and so did the bean counters in the government) that they could get this very capable aircraft and spread the cost of Anglicizing the aircraft over a larger number of airframes.  Thus the idea for the F-4M (or Phantom FGR Mk.2) was born. 

McDonnell had approached the RAF before with Phantom proposals to meet their needs.  In 1960 they had proposed model 98CJ (proposed as F-4H) which was essentially an F-4B with some modifications for the RAF.  It was to be powered by Rolls Royce RB-168 engines with cartridge starters, dual controls for transitional training, the shipboard catapult, wing fold, and arresting gear was to be removed and replaced by a lighter, non-retracting tail hook for emergency use, and increased internal fuel provisions.  Then in 1964 McDonnell proposed model 98EO (proposed as F-4E) which was essentially the F-4D with Rolls Royce RB168-25R engines.

So when the RAF showed interest, McDonnell was quick to give them a proposal.  On 21 January 1965 the specifications for the model 98GN (proposed as the F-4M) was finalized and given to the RAF, which was essentially the same as the F-4K that the Royal Navy had ordered, with the removal of some Navy specific equipment like the extending nose gear strut.  This resulted in an order for 150 aircraft.

One very interesting proposal came out of the RAF’s requirement for the ability to use the phantom to replace the Hunter and Canberra in the reconnaissance role.  Britain could not afford (or chose not to purchase) a dedicated reconnaissance version like the RF-4B or -4C.  But in McDonnell Report No. B617, dated 1 August 1966 and titled The Royal Air Force Phantom II, McDonnell showed two options to fill this role. 

The first option was a centerline pod which was about the size of the 600gal centerline fuel tank.  It was proposed that all the F-4Ms be built with the capability to use this pod.  The advantages of this system was that all the equipment could be moved from one aircraft to another as needed, repairs to the equipment could be performed without taking the aircraft out of service, and the aircraft would keep its full air-to-air capability.  The disadvantages were that the range would be reduced since there would be no centerline fuel tank, aircraft performance would be somewhat affected (although not much more than the centerline tank), and the aircraft, which already had very little room for added equipment, would have to have accommodate long cable harnesses to connect the pod to the newly added equipment for the cockpit and systems.

 
The second option McDonnell proposed was for a modification of the F-4M airframe to house the reconnaissance equipment internally.  This was model 98HT (proposed as RF-4M) and would add 2.65 feet just aft of the radome to house the cameras.  While this option would have increased range because it would be lighter than the F-4M with the recce pod, and it was able to carry a centerline fuel tank, this option was less desirable to the RAF because only the aircraft that were modified could fulfill the reconnaissance role; the modification would be more costly than the first option and thus fewer aircraft would be purchased with this option. Ultimately the modified aircraft would be less versatile since the FCS (fire control system) and AIM-7 Sparrow capability would be removed to make room for the reconnaissance equipment.  I assume that the RF-4M would retain its IR AAM capability.



 
Ultimately, due to the higher cost of the Anglicized version of the Phantom and pressing budgetary concerns, the RAF order was ultimately reduced to 116 aircraft and they chose to go with the EMI/McDonnell reconnaissance pod so that all the aircraft would be able to perform any task including reconnaisance.


Sources:
  1. McDonnell Report B617, dated 1 August 1966
  2. McDonnell List of Proposed Models, dated 1 July 1974
  3. Aeroguide 13 - McDonnell Phantom FG Mk.1 & FGR Mk.2, by Roger Chesneau
Revisions:

20 November 2013 - Original Post

Friday, November 1, 2013

This and that (nothing specific ...but more questions!)

In reading the book "Engineering the F-4 Phantom II - Parts into Systems" by Glenn E Bugos, I have run into some very interesting information.

1. The first item that raised questions in my mind was the designation F-4P.  I had never heard that variant before from any source and so it sent up red flags, and I need verification from at least one or two more sources before I believe it. To quote exactly what Mr. Bugos said:

"From their experience against SAMs and various NATO weapons in the hands of its Arab enemies, the Israelis devised a mysterious electronic warfare version, dubbed the F-4P.  Since some Israeli enemies were U.S. customers, Israel did not share every modification with the American military."

While I am sure there were quite a few modifications that Israel made to their aircraft that weren't shared with the U.S. military, I question the F-4P designation.  Israel didn't seem to put much stock into numeric designations, but rather used names to identify differing models.  In the case of the F-4 Phantom variants Israel used  Kurnass (F-4E), Tsalam Shabul (F-4E(S)), Kurnass Tsilum (RF-4E), and then Kurnass 2000, etc.

According to John Lake and David Donald in the fine work "McDonnell F-4 Phantom - Spirit in the Skies," the F-4P designation was at one time earmarked for the HIAC/PCC mockup that was later to become the never built F-4X program. (We know now that this ended up in the scaled back project that became the F-4E(S) Tsalam Shabul for Israel under Project Peace Jack).

Meanwhile, the whole idea that there still is an undocumented version of the Kurnass used for electronic warfare has peaked my interest.

2.   In his book Mr. Bugos also talks about the Navy's decision to delete the cannon armament and go with a completely missile armament on the F4H.  Here are what he gives as the reasons for that decision:
  1. Missiles and their associated equipment were much lighter than the cannons and associated equipment that they replaced.
  2. They were much cheaper than an aircraft. (you may be thinking at this point...duh, really?  But the reasoning here is that with cannon armament the aircraft has to get dangerously close to the target, which increases the possibility that the aircraft itself may be lost in a dogfight.)
  3. Self-guided missiles reduced the workload of the aviators (Navy pilots), who only had to mash a button in response to symbols on a radar screen, rather than engaging in a dogfight (see rationale in #2 above),
  4. The use of guided missiles allowed a more flexible reconstruction of the F4Hs interception system.
3. Another tidbit of information I found fascinating was the problems that early testing of the J79 engine in the F4H turned up.  It seems that on static (teathered) engine runs at high throttle settings the titanium and steel shingle panels, just aft of the engines, quickly fell apart and departed the aircraft due to cracks and fatigue from the sonic roar-induced vibrations of the engine.  That required a thickening of the panels and larger fasteners and washers to hold them in place.

4.  A Phantom by any other name.  It seems that just before the YF4H-1 roll-out, there was a vote taken of McDonnell and Navy personnel to choose the name for the new aircraft.  The choices offered were Sprite, Ghost, Goblin, Satan, and Phantom II.  (I guess Mr. McDonnell had a special interest in the spirit world to such a extent that the War Department, in June 1946, had reserved for Mr. McDonnell the names of inhabitants of the spirit world.)  Well the vote came in and the top two vote getters were Satan and Ghost. So how did it become Phantom II?  Well, the only vote that really counted was Mr. McDonnell's, so at the last moment he decided to call it Phantom II in honor of the jet fighter that had moved his company from making parts for other aircraft manufacturers to designing and manufacturing their own aircraft. (F-4 Sprite?????  I think not!)


References:
  1. Engineering the F-4 Phantom II - Parts into Systems, by Glenn E Bugos
  2. McDonnell F-4 Phantom - Spirit in the Skies, edited by John Lake and David Donald
Revisions:

11/01/2013 - Original Post
11/04/2013 - Added information from McDonnell F-4 Phantom Spirit in the Skies, to the F-4P designation.