Article 9095 of rec.aviation.military:
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From: jfb@usgp1.ih.att.com (Joe Baugher)
Subject: New Fighter Series--Grumman F-14 Tomcat (2 of 14)
Message-ID: <D131r9.6G2@ssbunews.ih.att.com>
Summary: General description of F-14A Tomcat
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Date: Tue, 20 Dec 1994 00:09:09 GMT
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The winning Grumman design (Design 303E) featured engines in separate 
nacelles, set well apart from each other so that damage to one of them 
would have minimal effect on the other.  The main central and rear 
area of the fuselage consisted of two separate engine nacelles joined 
together by a shallow flat area known as a "pancake".  At the extreme 
rear of the aircraft, this pancake is little more than a decking 
between the engine pods.  This leaves a deep tunnel between the 
engines which imposes a drag penalty.  However, it adds to overall 
lift, gives an extra attachment area for weapons pylons, and provides 
some additional fuselage space for fuel and equipment.  The rear part 
of the broad between-engines pancake is gently curved upwards to 
reduce both the supersonic trim drag and the negative zero-lift 
supersonic pitching moment.  There are door-type speed brakes at the 
rear of the pancake both above and below, the lower brake being split 
in two to accommodate the arrester hook.  At the extreme end of the 
decking are a large fuel dump pipe and housings for electronic warfare 
equipment.  

A similar arrangement was used in the Soviet MiG-29 and Su-27 
fighters, which were designed much later.  One of the problems with 
this configuration is that it puts the thrust line of each engine 
rather far outboard from the centerline, producing sudden and violent 
nose slices (rotation in yaw) in the event of an engine failure.  

Most of the aircraft structure was made of conventional aluminum 
alloys, with some components being made up of steel.  About 25 percent 
of the empty weight was made up of titanium alloy, which was used for 
the wing box, wing pivots, upper and lower wing skins, the intakes, 
rear fuselage skins, as well as the hydraulic lines.  

The wings feature variable sweep, ranging from a minimum of 20 degrees 
to a maximum of 68 degrees (which could be set manually on the ground 
to as much as 75 degrees for carrier stowage).  The variable-sweep 
wing panels are supported by a massive wing carry-through structure 
which spans the upper center section of the aircraft, terminating at 
each end in a large pivot point for the outer moveable wing panels.  
This carry-through structure is made from electron-beam welded 
titanium alloy.  The fixed wing glove structure forms a diamond-shaped 
surface.  The beam has slight dihedral to reduce the cross sectional 
area of the central fuselage, reducing drag and assisting in the 
area-ruling of the fuselage.  In order to maintain a snug fit between 
the trailing edge of the wing and the upper surface of the rear 
fuselage, the rear edges of the fixed wing glove uses a set of 
inflatable canvas bags.  Teflon paint on the underside of the wing 
help to ensure that there is minimal abrasion of these bags as the 
wings are extended or retracted.  

Wing sweep angle is automatically controlled by the air-data computer.  
Throughout the entire speed/maneuver regime, an automatic wing sweep 
program matches the sweep angle to the optimal position.  However, the 
system can be manually overridden by the pilot in an emergency.  
Should the wings get stuck in the fully-aft position, the F-14A can 
still land safely at 200 mph with 4000 pounds of fuel or at 166 mph 
with 2000 pounds of fuel, in spite of the fact that the wing flaps are 
inoperative when the wing is swept.  

The wing has no conventional ailerons, roll control being provided at 
low speeds by wing-mounted spoilers and at high speeds by the 
differentially-moving horizontal tailplane.  The full-span trailing 
edge flaps have a small inboard section and a larger outboard section.  
These flaps are deliberately made inoperative when the wing is swept 
back to prevent damage.  Leading-edge maneuvering slats occupy 
virtually the full span of the outer wing panel leading edge.  To 
improve combat maneuverability, the slats and outboard flap sections 
can be deployed while the wing is in the fully-forward position.  When 
wing sweep is greater than 57 degrees, the wing spoilers are locked 
down, and roll control is provided completely by the 
differentially-moving horizontal stabilizers.  

Air is admitted to the engines via two large, rectangular-shaped, 
sharp-lipped intakes, one mounted on each side of the fuselage.  The 
edges of the intakes are swept sharply backward from top to bottom, 
ensuring that adequate amounts of air get into the engine at high 
angles of attack.  These intakes are mounted well outboard of the 
fuselage sides, far enough away that turbulent boundary layer air is 
kept from entering the engine without the use of complex diffuser 
systems such as those fitted to the F-4 Phantom.  Because of the 
overall dihedral of the wing glove box, the intakes are canted 
outwards at the bottom.  However, even at the top of the intakes where 
they are closest to the fuselage, the inner wall of the intake is 
still at least 8 inches away from the fuselage.  

The intakes are of multi-ramp wedge configuration and offer a straight 
path for the air entering the engines.  Each intake has a pair of 
adjustable ramps attached to the upper part of the inner intake.  
Hydraulic actuators in the upper part of the intake adjust the 
positions of the first and second ramps in the upper surface of the 
inlet and of the diffuser ramp located further aft, reducing the inlet 
air to subsonic velocity before admitting it to the engine.  A gap 
between the back edge of the second ramp and the leading edge of the 
diffuser ramp allows bleed air to escape from the inlet, passing 
overboard via a bleed-air door in the outer surface of the inlet.  The 
inlet ramps are under the automatic control of a computer, which 
calculates the optimal position for the ramps based on engine speed, 
air temperature, air pressure, and angle of attack.  At supersonic 
speeds, the hinged panels narrow down the throat area while diverting 
the excess airflow out of the ducts through aft-facing spill doors at 
the top of the intakes.  At low speeds (especially during takeoff) 
when more engine air is needed, this airflow is reversed and extra air 
is sucked in.  

Two small triangular-shaped vanes were mounted on the leading edge of 
the wing gloves.  These vanes are normally retracted, but are extended 
at supersonic speeds under the control of the air-data computer.  The 
purpose of these vanes is to generate additional lift ahead of the 
aircraft's center of gravity, which helps to compensate for a 
nose-down pitching moment that takes place at supersonic speeds.  
These vanes are automatically deployed when the speed exceeds Mach 1.4 
in order to push up the nose and unload the tailplanes, giving them 
enough authority to pull 7.5 g at Mach 2.  The vanes can be manually 
deployed between Mach 1 and Mach 1.4, but will not operate when the 
wing sweep is less than 35 degrees because that would lead to too much 
pitch instability at low speeds.  

The original Design 303E featured a single tall vertical fin and a 
folding ventral strake.  At Navy insistence, Grumman switched to a 
twin-tail configuration at the last minute and replaced the large 
folding strake with two smaller fixed strakes mounted underneath each 
engine nacelle.  Each of the twin tail fins holds a conventional 
rudder for yaw control.  The twin tail fins provide an effective means 
of countering destabilizing flow generated by the air intakes during 
sustained flight at high angles of attack.  In addition, the dual 
rudders have the added advantage of reduced height for carrier 
stowage.  

The two-seat, tandem cockpit is enclosed by a single-piece 
clamshell-type canopy.  The pilot is in front, and the radar intercept 
officer is in the rear.  The crew members sit on Martin-Baker GRU-7A 
rocket-propelled ejector seats which can be used from zero 
altitude/zero airspeed up to 450 knots airspeed.  There is minimal 
duplication of controls and instruments for the pilot and the radar 
intercept officer.  The pilot has three displays for viewing flight, 
navigation and tactical data, including armament controls and flight 
instruments.  The aft cockpit has controls and displays for the AWG-9 
fire control system.  The back-seater operates the radar, identifies 
the adversary, and guides the pilot in making an effective 
interception.  Unlike in the Phantom, either crew member can fire a 
missile.  

The engines for the F-14A are a pair of Pratt & Whitney TF30-P-412 
axial flow turbofans, each rated at 12,350 lb.s.t.  dry and 20,900 
lb.s.t with afterburning.  The TF30-P-412 was essential similar to the 
TF30-P-12 that had been used for the F-111B.  The exhaust features a 
variable-geometry nozzle with movable petals which slide on curved 
tracks to close down to minimum area for subsonic cruise and fully 
opened to a convergent and then divergent profile for afterburning 
flight during takeoff and at supersonic speeds.  

The F-14 employs a system known as Direct Lift Control (DLC) for 
automatic control of attitude during carrier landings.  When DLC is 
engaged, the spoilers on the upper wing pup up into what is known as 
the "neutral" position.  When these spoilers are lowered, instant lift 
is generated with no need for an attitude change.  

For its primary interception role, the F-14 is equipped with the 
Hughes AN/AWG-9 radar fire control system.  The AWG-9 has the ability 
to carry out near-simultaneous long-range missile launches against up 
to six targets while tracking 24 more.  The antenna is a 36-inch flat 
plate unit.  The IFF antennae are mounted directly on the plate and 
take the form of an array of dipoles.  the output power is 10.2 
kilowatts.  The AWG-9 can look down into ground or sea clutter, 
detecting and tracking small targets flying at low level.  The clutter 
is removed by a signal processor which uses analog filtering.  

The single-wheeled main landing gear elements retract forwards into 
wells inside the wing glove, rotating 90 degrees to lie flat.  The 
twin-wheeled nose unit retracts forward into a well in the nose.  

Integral fuel tanks are provided between the wing spars of the outer 
section, holding 295 US gallons each.  The tapering section of the 
rear fuselage aft of the wing carry-through structure carries an 
additional 648 US gallons of fuel, and a 691-US gallon tank is fitted 
between the cockpit and wing carry-through structure.  Two feeder 
tanks combined offer a 456-gallon capacity, bringing total internal 
fuel capacity to 2385 US gallons.  A 267-gallon external drop tank can 
be carried on hardpoints underneath each air intake.  The Tomcat is 
equipped for in-flight refuelling via a retractable probe on the 
starboard side of the fuselage.  

Early Tomcats were equipped with a gimbal- mounted AN/ALR-23 infrared 
detection set mounted underneath the nose that could be slaved to the 
radar or used independently to scrutinize areas not searched by the 
radar.  Its indium antimonide detectors were cooled by a 
self-contained Stirling-cycle cryogenic system.  In practice, this IR 
sensor proved to be ineffective, and was replaced by the Northrop 
AXX-1 Television Camera Set (TCS), which consists of a television 
camera fitted with a stabilized telephoto lens.  Displays appear on 
both the pilot's and the WSO's control panels.  The system can be used 
to spot an enemy visually and to identify him early, hopefully 
preventing Tomcat pilots from shooting down friendlies.  The first 
production installation of the TCS was incorporated in 161597, the 
first Block 125 aircraft.  

The Central Air Data Computer (CADC) is an AiResearch CP-1166B/A.  It 
uses data from sensors which measure pitot and static pressures, air 
temperatures, and angle attack to select the optimal wing sweep angle 
and sends commands to the control surfaces.  It also passes to the Air 
Inlet Control Systems (AICS) the information it needs to set the inlet 
ramps to their optimal positions.  

The AN/ARA-63 aircraft approach control system uses the AN/SPN-41 and 
the AN/TRN-28 transmitting sets.  It provides primary or backup 
instrument approach capability.  

The spine of the Tomcat contains blade antennae for the UHF/TACAN and 
data link/IFF.  Radio and navigation equipment on board the aircraft 
include the APX-71 IFF transponder, AXX-76 IFF interrogator, ARC-51 
(later switched to ARC-159) UHF radios, ARR-69 auxiliary receiver, 
KY-58 cryptographic system, ASN-92 CAINS II (Carrier Aircraft Inertial 
Navigation System II) inertial navigation system, APN-154 beacon 
augmenter, APN-194 radar altimeter, Gould ARN-84 TACAN and ARA-50 
automatic direction finder.  

A Harris ASW-27B digital datalink provides high speed data 
communication between the Tomcat and ship-based command and control 
systems.  This system can also be used to link to the Airborne 
Tactical Data Systems of Grumman E-2C Hawkeye early warning aircraft.  
This system can be used to pass target data back and forth between 
aircraft, extending the effective radar range.  

The Tomcat initially carried APR-25 and APR-27 radar warning 
receivers.  These have largely been replaced by the Magnavox ALR-50 
which is designed to warn crews of SAM launches.  A major upgrade 
updated this equipment to deal with the SA-6 *Gainful* missile and its 
associated *Straight Flush* radar.  The Tomcat is equipped with the 
Goodyear ALE-39 chaff and flare dispensing system, which has replaced 
the ALE-29 originally carried.  The Tomcat entered service with the 
Sanders Associateds ALQ-100 noise deception jammer, but this has been 
replaced with the Sanders AN/ALQ-126A.  

Next: A description of the armament of the F-14A.

Sources:

   Grumman Aircraft Since 1919, Rene J. Francillon, Naval Institute
   Press, 1989.

   Grumman F-14 Tomcat, Doug Richardson, Osprey, 1987.

   F-14 Tomcat: Fleet Defender, Robert F. Dorr, World Airpower
   Journal, Vol 7, 1991.
 
   Grumman F-14 Tomcat Variant Briefing, World Airpower Journal,
   Vol. 19, 1994.

   The American Fighter, Enzo Angelucci and Peter Bowers, 
   Orion, 1987.

   Encyclopedia of World Military Aircraft, Volume 1, David Donald
   and Jon Lake, AirTime, 1994.

   The World's Great Interceptor Aircraft, Gallery Books, 1989. 


Joe Baugher			  **************************************
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