Smart Plane, Dumb Bombs, Bad Maps?: Part Two

Back to Part One

Designed around bleeding-edge 1960s avionics  the F-111 was built to would take the guesswork out of high speed, low-level navigation. Its avionics included an inertial navigation system (INS), terrain-following and attack radars, and a navigation computer that used these inputs to determine the airplane’s current location. Since an INS tends to drift over time, due to small errors in the measurements made by its gyros and accelerometers, the F-111’s navigator provided updates by taking a radar fix on a nearby landmark, usually known as an offset aimpoint, or OAP. Though they might be taken for granted by an observer, the entire process was dependent on good maps and geodetic information. F-111 pilot Richard Crandall’s description of Operation EL DORADO CANYON, the 1986 air attacks on Libya, explains what could go wrong when the F-111 flew with bad information.

Three groups of F-111Fs were involved in the operation, two equipped with laser-guided bombs (LGBs) and a third – attacking Tripoli airport – with “dumb” bombs that would be slowed by ballutes to allow for low-level delivery. All carried the PAVE TACK laser-designating pod, which also included an infra-red camera.

An F-111F aircraft releases Mark 82 bombs equipped with ballutes over a training range in 1986. Air Force photo via Wikimedia Commons

An F-111F aircraft releases Mark 82 bombs equipped with ballutes over a training range in 1986. Air Force photo via Wikimedia Commons.

Crandall focuses on the attack on Tripoli airport, where five aircraft carrying seventy-two bombs reached Tripoli airport but only one succesfully hit the Libyan aircraft parked on the tarmac. Why? According to Crandall, the attacking planes had been provided with the distance between a very visible radar target at the airport and where their bombs were supposed to land (“the radar offset”), and that information was wrong.

The aircrew that hit the airport, hats off to them! I knew the WSO extremely well, a good friend and fellow instructor for several years. In watching his tape, he nailed the radar offset for the airport. The radar was not good at burning out flat concrete but did much better on targets with more radar reflectivity. He went to narrow sector expand mode on the offset and then switched back to the Pave Tack infrared video, and nothing appeared. He went back and checked the offset again, and still dead on. The he switched back to the Pave Tack. Every other aircraft let the bombs fly using the radar offset. Their bombs hit the airfield between the taxiway and the runway. The coordinates on the offset were evidently bad. My friend went from narrow sector to wide sector in the Pave Tack and in the right side edge of the field of view he caught sight of the IL-76s. You hear him shout “come right come right” to the Pilot who is seeing nothing except tons of anti-aircraft artillery exploding and his TFR screen. The pilot made a hard turn. As he rolls out, his WSO has fired the lasers and the bombs immediately flew off. You see in the video the Pave Tack’s video rotate to upside down due to the mechanics of the pod rotating to see the target behind the aircraft. The WSOs had to learn how to track upside down when guiding LGBs. You then see a huge explosion rip through the airplanes. That was incredible teamwork in the cockpit. Good on the WSO to switch to wide field of view—it went from a really narrow straw to a slightly fatter straw to look through, but got him onto the target.

All the aircraft attacking the Tripoli area seem to have had trouble with navigational updates, not just those at the airport. The final update by radar OAP before crossing the Libyan coastline was the island of Lampedusa, and the aircrew were given coordinates for their OAP that were off by several hundred feet. James A. Jimenez, who flew one of the F-111s attacking Bab al-Aziziyah, wrote his recollections of the mission for the December 2008 issue of Air and Space Magzine. He remembers the last radar update point as being a tower at the western tip of Lampedusa.

Our navigation system had been running sweet, but when Mike [his WSO] selected the tower, the cursors fell about one mile to the west. An error during the planning process had resulted in incorrect coordinates being issued to all crews. Mike recognized the error and did not use the coordinates to update our navigation system. His decision was probably the single greatest factor enabling us to hit our target: those who updated their nav systems based on the bad coordinates missed.

Among those who ran into trouble was one F-111 targeting the Bab al-Aziziyah barracks whose error at Lampedusa was compounded upon reaching Tripoli and which ended up a mile and half off target. Its bombs ended up hitting and damaging the French embassy.

I’m still not entirely clear on where the offset coordinates for EL DORADO CANYON came from. According to an official US Air Force history, during the F-111s first combat deployments to Vietnam the offset aiming points came from a photo-positioning database called SENTINEL DATE at the Defense Mapping Agency Aerospace Center in St. Louis, or an equivalent database called SENTINEL LOCK that was deployed to Takhli and Nakhon Phanom air force bases in Thailand. SENTINEL DATE/LOCK “provide[d] a menthod for precisely determing the latitude, longitude, and elevation of navigational fix-points, offset aim points, and targets.”

However, a student paper for Air Command and Staff College by Major James M. Giesken explains that the update points for EL DORADO CANYON were geolocated by the F-111 fighter wing staff using the Analytical Photogrammetric Positioning System (APPS), an analog system for determing the location of an object on photo imagery. APPS’s output used the WGS 84 standard datum, while the target coordinates were expressed in the European Datum used by American units in Europe, and this was the source of the location error. (There’s no source for that information in the paper, but Giesken was an instructor at the Defense Mapping School from 1986 to 1988, then aide to the director of the Defense Mapping Agency for fourteen months and executive officer for the director for another seventeen. Hopefully he had a good source for the information.)

The Analytical Photogrammetric Positioning System. From Army Research & Development, May-June 1976, p.24

An early version of the Analytical Photogrammetric Positioning System. From Army Research & Development, May-June 1976, p.24

What happened during Operation EL DORADO CANYON demonstrated the obstacles to accuracy that could not be erased by the use of advanced technology, whether in a bomb or an airplane. Regardless of the precision in the weapon, an attack was only as accurate as the underlying information – and problems with that information could end up embedded in the relationships between the very systems that were supposed to provide a more precise attack than ever before.

Smart Plane, Dumb Bombs, Bad Maps?: Part One

At The Drive‘s “War Zone” (and, before that, Gizmodo‘s “Foxtrot Alpha”) Tyler Rogoway has been regularly posting first-hand reflections on flying military jets. The latest, by Richard Crandall, covers the F-111 Aardvark, probably the leading all-weather strike aircraft of the Cold War. Designed around bleeding-edge 1960s avionics that would take the guesswork out of high speed, low-level navigation, the F-111 ended up being caught between the limits of its technology and the development of a newer generation of weapons. At the same time, its combat debut pointed to the limits of the entire system of navigational tools that military aircraft have been using ever since.

General Dynamics F-111F at the National Museum of the United States Air Force. (U.S. Air Force photo)

General Dynamics F-111F at the National Museum of the United States Air Force. (U.S. Air Force photo)

The F-111 was built to penetrate enemy airspace at low level regardless of rain, fog, or darkness. How low? Crandall recalls that “sometimes we would be flying low through the mountains of New Mexico or southwest Texas and the jet’s external rotating beacon would flash off the terrain that we were flying by and it would seem to be right next to the wingtip. Some aircrew would turn it off as it unnerved them.”

The airplane’s avionics were supposed to be interconnected to make the attack process practically automatic. While the F-111’s terrain-following radar (TFR) kept the plane 200 feet above the ground, the autopilot flew the plane from waypoint to waypoint. Upon reaching the target, the ballistics computer automatically released the F-111’s bombs when the plane reached the correct parameters (position, airspeed, delivery angle, etc.). Or, if the crew put it into manual mode, the computer showed the pilot a “continually computed impact point” (CCIP) that adjusted for wind and drift to indicate where the bombs would land if they were released at that moment. In the planned ultimate version of the F-111, the F-111D, all this equipment would be integrated in to a fully digital computer system complete with “glass cockpit” multi-function electronic displays. Even the other versions of the F-111 that flew with fully or partly analog systems included similar systems.

At the heart of the system was the airplane’s inertial navigation system (INS), a package of gyroscopes and accelerometers that provided an ongoing track of the airplane’s location. Because the INS drifted by about half a nautical mile every hour, the F-111 required regular position updates to keep itself on course. The problem of correcting for INS drift wasn’t unique to the F-111. Ballistic missile submarines updated their INS using a fix from the Loran-C radio or Transit satellite network. Tomahawk missiles used an onboard terrain-matching system called TERCOM.The Strategic Air Command’s variant of the F-111 carried an Litton ASQ-119 Astrotracker that took position fixes based on the locations of up to fifty-seven stars, day or night (as well as a more accurate INS that used an electrostatically suspended gyro).

The tactical F-111 usually took position updates by locking the non-TFR attack radar onto a pre-selected terrain feature with a known position and good radar reflectivity (called an offset aimpoint, or OAP). When everything worked, that gave the F-111 remarkable accuracy. As F-111 WSO Jim Rotramel remarked to writers Peter E. Davies and Anthony M. Thornborough for their book on the F-111, “if the coordiantes for various offset aim-points (OAPs), destinations and targets were all derived from accurate sources, the radar crosshairs were more likely to land neatly on top of them.”

Even if some parts of the system failed, the remaining elements were good enough to let the F-111 complete the mission. As Crandall explains:

Our inertial navigation system was nice, but we trained to use dead reckoning and basic radar scope interpretation to get to the target even without the INS. We had backups to the backups to the backup. INS dead? Build a wind model and use the computers without the INS. That doesn’t work? Use a radar timed release based on a fixed angle offset. We practiced them all and got good at them all.

The navigator could even use the raw, unprocessed data from the TFR, a truly terrifying process that Crandall calls a “truly a no-kidding, combat-emergency-only technique.”

Trouble with the F-111Ds avionics, which proved too ambitious for the time, meant that the US Air Force flew three other versions of the plane while trying the debug them. The first was the F-111A, which had an all-analog cockpit; the -E (Crandall: “basically an F-111A with bigger air inlets”), which added a few features; and the -F, which added more digital equipment but not the full suite of the features designed for the -D. The last of these was also upgraded to operate the PAVE TACK pod that let the plane drop laser-guided bombs (LGBs). LGBs put the terminal “smarts” for precision bombing into the weapon itself, with the bomb following laser energy reflected off the target from a beam in the PAVE TACK pod.

The US Air Force Museum in Dayton, Ohio, has a 360-degree photo of the cockpit of the F-111A in their collection here. It’s all switches and gauges, with no screens apart from those for the radar.

However, even with laser-guided bombs, the F-111F still needed the airplane’s avionics to get to the target, and those systems remained dependent on maps and geodetic information in order to ensure that INS updates and OAPs were accurate. In 1986, that would prove to be the weak link during the F-111’s combat debut.

To Part Two (soon)

A Return to Previously Scheduled Service

Work and life mean that this blog has been silent over the summer. I’m hoping to get back to it shortly, but in the meantime here’s some interesting reading – all available free online – to tide you over.

The Getty Research Portal is now collating links to books in fine arts and art history from twenty-two libraries, including the Getty Foundation’s own libraries and the Metropolitan Museum of Art. Alongside rare out-of-copyright titles, several of the contributors are also putting up their own recent books and catalogs. You could already access many Getty publications at the Getty Publications Virtual Library and Metropolitan Museum publications through MetPublications, but the Portal promises to bring access to more titles in one place.

Knowledge Unlatched has announced the extensive list of titles being included in their 2016 round. Almost all the books from the 2015-16 Round 2 are now available through their website. Books are made Open Access through KU by libraries paying the publishers (including my own employer), so many thanks are due to those institutions for stepping up and making this possible.

The University of Alberta Press has not only acquired the full backlist of the the Canadian Circumpolar Institute Press but has digitzed them and made them available online. CCI Press will now become UAP’s Polnya Press imprint. First books have been annouced and are coming out now.

Last, but certainly not least, University of Calgary Press continues to publish its books under the Creative Commons BY-NC-ND license. I have their history of Alberta in the First World War, The Frontier of Patriotism, on my phone right now.

Beyond Timbuktu

One has to be a little nervous about any book whose description of its own first chapter says that “it might be of interest to specialists but can probably be skipped by the average educated reader who does not know Arabic.”

Beyond Timbuktu: An Intellectual History of Muslim West Africa is certainly a book that’s best suited for the specialist, though it does contain a lot of interesting information. Ousmane Oumar Kane ranges widely over the history of Muslim education in West Africa, focusing mostly on the eighteenth and nineteenth centuries but reaching forwards to contemporary Islamic colleges and universities in Africa and back into the Middle Ages.

The latter caught my attention for the usual spate of connections between distant regions. One I already knew was the pilgrimage to Mecca in 1324/25 of the Malian emperor Mansa Musa, a king so rich he was immortalized (in European style) as an ornament on the famous Catalan Atlas. One I had never heard of was the existence of a school in Cairo for students from Borno, near Lake Chad, endowed in the mid-thirteenth century by merchants from the region.

Though most of the literature Kane discusses is Arabic, he also mentions the phenomenon of ajami, African languages transcribed in the Arabic alphabet. I was surprised to read that ajami may have appeared as early as the twelfth century, and that ajami literature exists in twenty-nine languages in West Africa and more than eighty throughout Africa.

It always interesting to get a little prod in one’s blind spot, since I really shouldn’t have been surprised at all. I already knew that appropriating one alphabet to write another language was a medieval commonplace. Christians in Muslim Spain wrote Latin and Spanish (or what would become the latter, over time) in Arabic script, usually called mozarabic. Muslims and moriscoes (converts from Islam) in Christian Spain did the same, called aljamia (sharing the same root as ajami). Judeo-Persian (which is more Persian than Hebrew) is written with Hebrew script, as are Judeo-Arabic and Ladino. Why shouldn’t the same be true in West Africa?

Another “Smallest Aircraft Carrier”

At 131-feet in length, the helicopter landing trainer Baylander (IX-514) has been billed as the “smallest aircraft carrier” in the US Navy, if not the world, by the Navy itself, its current owners the Trenk Family Foundation, and, well, me. That claim is based on the more than 10,000 helicopter landings on the Baylander between 1986 and its retirement in 2014. But what if you want the smallest ship to regularly launch its own aircraft?

The November 1963 issue of Navy magazine All Hands crowned the 206-foot USS Targeteer (YV-3) as the fleet’s “smallest aircraft carrier.” A Drone Aircraft Catapult Ship, the Targeteer was equipped to launch and recover target drones used for gunnery practice by the fleet. The third Landing Ship, Medium (LSM) to be converted into a drone launching ship, the Targeteer was based in San Diego from 1961 to 1968, replacing the USS Launcher (YV-2, 1954–1960) and the USS Catapult (YV-1).

USS Targeteer insignia. NH 64878-KN (NHHC photo).

USS Catapult, circa 1955. NH 55065 (NHHC photo).

USS Catapult, the Targeteer‘s sister ship, circa 1955. NH 55065 (NHHC photo).

Even Targeteer‘s claim, though, is contested. The Executive Officer of the fleet tug USS Kalmia (ATA-184), which also launched and recovered drones at San Diego, wrote to All Hands to claim that its length of 143 feet entitled it to the title of “smallest aircraft carrier.” (All Hands deferred to the Navy’s official classifications. The Targeteer was a Drone Aircraft Catapult Ship, the Kalmia just an Auxiliary Ocean Tug.)

USS Kalmia underway on 16 January 1964. NH 102803 (NHHC photo).

USS Kalmia underway on 16 January 1964. NH 102803 (NHHC photo).

All three claims are weak if you are looking for a ship that launches and retrieves multiple aircraft. If, on the other hand, you are looking for the smallest Navy-crewed vessel which could land or launch a single aircraft, Baylander, Targeteer, and Kalmia all lose to the helicopter pad-equipped “Tango boats” of the Mobile Riverine Force in Vietnam. Officially designated Armored Troop Carriers (ATC)s, these were Landing Craft, Mechanized (LCM) that were modified to serve as floating armoured personnel carriers in the Mekong Delta. Some were further modified with a steel flight deck on top that ran pretty much the full length of the boat. The first helicopter landing on one of these Armored Troop Carrier (Helicopter), or ATC(H)s, took place on July 4, 1967. At 56-feet in length, which is more or less the length of a Huey helicopter, I doubt I’ll find anything smaller to claim the title.

 A U.S. Army UH-1D helicopter lands on the helicopter pad of a modified U.S. Navy Armored Troop Carrier (ATCH R-92-2) operating as part of the Riverine Mobile Force, 8 July 1967. Photography by Photographer's Mate Second Class Edward Shinton. USN 1132291 (NNHC photograph).

A U.S. Army UH-1D helicopter lands on the helicopter pad of a modified U.S. Navy Armored Troop Carrier (ATCH R-92-2) operating as part of the Riverine Mobile Force, 8 July 1967. Photography by Photographer’s Mate Second Class Edward Shinton. USN 1132291 (NNHC photograph).

The Last of the Computers

One of the first hires at the Jet Propulsion Laboratory (JPL) in Pasadena, before JPL became a NASA facility and even before it had the name JPL, was Barbara Canright. Canright was employed as a “computer” who would do complicated and repetitive mathematics for JPL’s engineers, as were many women who followed in her footsteps at JPL.

From the nineteenth century until the 1960s, many large-scale scientific and engineering project relied on human computers – often female university graduates without the same employment opportunities as their male counterparts – to handle the computational load. As Nathalia Holt explains in her recent book Rise of the Rocket Girls, JPL was no different. Holt’s book describes the careers of computers at JPL from the 1940s to the present: one of the last computers to be hired, Susan Finley, still works at the laboratory.

The book does an excellent job narrating the personal trials and professional triumphs of these women, including the disappearance of computing by hand. By the time JPL acquired its name in 1943, multi-purpose electronic computers were only a matter of years away. In the 1950s, JPL’s computing department acquired the first of many IBM mainframes to do calculation work. “Cora” (for Core Storage) was given a woman’s name to fit into the all-female group. Many of the women who worked with it soon branched out into programming in FORTRAN and other languages, at a time when programming had little or none of the prestige which it would later acquire. That decision helped them carve out a niche which survived when hand calculation was eliminated as a trade by the electronic computers, leading to the computer department being renamed Mission Design and the women who had worked there eventually retitled as engineers. Rise of the Rocket Girls describes their ongoing contributions to a list of JPL space probes that includes Ranger, Mariner, Viking, and Voyager.

It’s an interesting story not least because the female calculators employed at JPL were among the last in the business. Their success in transitioning into the Computer Age, reflected both in their success as individuals and in the establishment of Mission Design, was loaded with assumptions about how the aerospace industry valued various kinds of work. Though Holt doesn’t linger on them, in a lot of ways the undercurrents in Rise of the Rocket Girls reminded me of Rebecca Slayton’s Arguments that Count, which examined the relative influence of physicists and computer scientists in planning for ballistic missile defense during the same era.


The Impact of Middlebrow Architecture

From The Sound of Freedom: Naval Weapons Technology at Dahlgren, Virginia, 1918-2006:

The most conspicuous example of the early 1960s effort to make Dahlgren look more like a modern science installation rather than a gun range was the construction of the Computation and Analysis Building (Building 1200). ‘K’ Laboratory had been in need of office space for some time … Consequently, [Ralph A.] Niemann and [Charles J.] Cohen, with the early support of [Naval Weapons Laboratory] commander Captain Manley H. Simons Jr., began lobbying for a new office building at Dahlgren, using POLARIS, Naval Space Surveillance Command, and TRANSIT as justification for the additional work space … Designed by Dahlgren engineer Robert Ryland, the Computation and Analysis Building was (and remains) situated near the station’s front gate, well away from the Potomac and the gun range. There was no mistaking it for a testing shed. It really looked like a science building with its graceful lines and large windows, standing in sharp contract to the rest of NWL’s research plant. It was no mistake that the building was at the front gate, as it was intended to instill visitors coming to Dahlgren with a sense of scientific enterprise. The strategem worked. ‘One the building was constructed,’ said Niemann, ‘then the issue about closing Dahlgren sort of went away because when people would come down, they’d see a new building. They’d figure things were going good, and maybe Dahlgren shouldn’t be closed.'”

The photograph of the Computation and Analysis Building in The Sound of Freedom shows a pleasant but unremarkable low-rise office building.

James P. Rife and Rodney P. Carlisle, The Sound of Freedom: Naval Weapons Technology at Dahlgren, Virginia, 1918-2006, p. B-3

From James P. Rife and Rodney P. Carlisle, The Sound of Freedom: Naval Weapons Technology at Dahlgren, Virginia, 1918-2006, p. B-3

The previous decade had saw the appearance of a swathe of new corporate research and development centers with innovative architecture, often designed both to streamline the collaborative research process and to put an impressive, even futuristic, face on corporate America. The Eero Saarinen-designed GM Technical Center is the most famous of these, but many of the research campuses were built by companies in the aerospace and defense sectors. In 1957, TRW’s Space Technology Laboratories (architect, A.C. Martin) opened in Los Angeles; the next year Convair Astronautics built a new headquarters designed by Pereira and Luckman just outside San Diego.

The NWL Computation and Analysis Building was a far more modest building. Instead of glass curtain walls, it had ribbon windows. Instead of a landscaped campus, it had a lawn. Its designer, Robert Ryland, was an electrical engineer who had held series of management roles in the various NWL labs. According to his obituary in the Fredericksburg Free-Lance Star, Ryland graduated from MIT in 1951 and and headed the Electronics Systems, Strategic Systems, Protection Systems, and Personnel departments at Dahlgren before retiring as head of the Engineering and Information Systems Department in 1992.

There’s no real comparison between the Computation and Analysis Building and the big private research campuses, but there’s a entertaining overlap of eras and impact. Clearly, if Ralph A. Niemann is to be believed, you didn’t need a star architect or an expensive and expansive campus to make an impression if you were working in government.

Source: James P. Rife and Rodney P. Carlisle, The Sound of Freedom: Naval Weapons Technology at Dahlgren, Virginia, 1918-2006 [GPO, 2006] p. 119-120)