Attrition: F-16s Survive Hinge Pin Failure


April 14, 2021: On February 11, 2021 Belgium’s fleet of elderly 43 F-16As and eight two-seat F-16Bs was grounded after one of the F-16As lost its engine, which overheated and partially disintegrated. The pilot was able to turn around and make an emergency landing. Within a week the problem was found to be a defective hinge pin in the F-100 engines used by Belgium F-16s. Many Belgium F-100 engines needed to go through a five-day engine modification process to replace the hinge pins and any other engine components that had suffered excessive heat exposure because of the hinge pin problem. The hinge pin problem was not widespread because simple components like hinge pins are purchased from a wide variety of suppliers. Even simple items like hinge pins must meet stringent standards and some batches can appear to meet the standards but don’t. Selling substandard or counterfeit components has become a big business since the 1990s, with China and Russia being the source of some very convincing counterfeits. Jet engines have hundreds of parts that wear out frequently and the bad batch of components is a constant threat, Some Belgium F-16s are already back in service within a week and by mid-March all were all 51 Belgium F-16s were cleared for service. This was just in time for a veteran Belgian F-16 to become the first European pilots to have flown an F-16 for 5,000 hours. Only five other pilots have done that.

Belgium earlier decided to replace its F-16s with 34 F-35A stealth fighters. These won’t begin arriving until 2025 and delivery will not be complete until the end of the decade. At that point there won’t be many, if any, customers for 40-year-old F-16s, no matter how well maintained they are.

In Belgium engine MRO (Maintenance, Repair and Overhaul) is performed by Belgium firm Patria, which is a major provider of MRO for F-100 engines used by European air forces. There are a lot of these engines around because they are very popular, durable and reliable. F-100 entered service in 1974 for the F-15 (which uses two of them) and then for the F-16 and some other aircraft. The F-100 engine is expected to continue in use into the 2040s. The engine design has been upgraded several times since the 1980s and even with regular MRO an F-16 will serving 20-30 years will wear out two or three F-100s during that time. Two American firms manufacture the engine as the F-100 and F-110 and compete with each other for sales. These two-ton engines cost about $5 million brand new. MRO costs over engine lifetime doubles or triple the purchase cost. The F-100/110 is five meters (16 feet) long with a maximum diameter of 1.2 meters and produces up to 29,000 pounds of thrust.

The Netherlands F-16s, which also use Patria for MRO, had their engines examined and found no evidence of the problems in the Belgium F-16s. The Netherlands Air Force covered for Belgium to provide quick-reaction fighters the two nations that share air defense duties for their air space.

Belgium received most of its F-16A in the early 1980s and these fighters have been heavily used since 2001 to support NATO operations against terrorism and to supply more air interception missions against growing Russian air force activity against new NATO members in eastern Europe. Belgium F-16s underwent major upgrades to Block 20 standards in the late 1990s and this took nearly a decade to complete. Most of those new NATO members replace their Russian Cold War era fighters with F-16s, usually Block 30 or better models.

Engines aren’t the only problem elderly F-16s have to deal with. In late 2014 Norway confirmed reports that some of their older F-16B fighters had been found to have cracks in the fuselage and some of these F-16B two-seat models were grounded until repairs could be made. Earlier the United States had found similar cracks in some of their F-16D aircraft and after investigating concluded that all F-16Ds and F-16Bs, which the U.S. does not use any more, should be inspected. At the time there were over 150 F-16B and 400 F-16D aircraft in service worldwide. Turkey, Israel, Belgium, the Netherlands, Pakistan, Denmark and Norway have some of these aircraft and all had to inspect for cracks. Only Norway reported finding any, other may have just quietly done the inspections and made repairs as needed. The situation in Norway was quickly noticed because some of the F-16Bs involved are stationed at the air base the normally sends F-16s aloft to intercept Russian recon aircraft getting too close.

This crack crises began in mid- 2014 when the U.S. Air Force grounded 82 F-16D jets after cracks were discovered in longerons (metal support beams inside the forward fuselage, which hold the cockpit in place). The D version of the F-16 is the two-seater used for training. Some 16 percent of the 969 F-16s in the U.S. Air Force are the D model and these are all at least 24 years old with more than 5,500 hours in the air. The longeron design for the D and B models is different than that for the single seat models because the D and B models have a longer cockpit canopy. The air force made repairs and replacements to put the grounded F-16Ds back in service. The manufacturer has repair kits for the F-16Bs, which are the two-seater version of the F-16A. Norway has 57 F-16s, ten of them the B model.

Even in 2014 it was noted that the U.S. F-16 fleet was rapidly aging. The average age of existing F-16s is over 30 years, and the average aircraft has nearly 7,000 flight hours on it. Most European nations received their F-16s in the 1980s and have upgraded them since. But they are still basically elderly aircraft. Back in 2009 the first Block 40 F-16 passed 7,000 flight hours. In 2008 the first of the earliest models (a Block 25) F-16 passed 7,000 hours in the air. The F-16C was originally designed for a service life of 4,000 hours. But advances in engineering, materials and maintenance techniques have extended that to over 8,000 hours. Because of the wars in Iraq and Afghanistan, F-16s sent to these areas will fly over a thousand hours a year more than what they would fly in peacetime.

The F-16 thus follows the path of previous best-selling fighters. During the Cold War (1947-91) Russia built over 10,000 MiG-21s and the U.S over 5,000 F-4s. Since 1991 warplane manufacturing has plummeted about 90 percent. However, the F-16 has been popular enough to keep the production lines going strong into the 2020s. The U.S. still has about a thousand F-16s in service (about half with reserve units). F-16s built so far went to 27 countries. America has hundreds in storage, available for sale on the used warplane market. The end of the Cold War led to a sharp cut in U.S. Air Force fighter squadrons. Moreover, the new F-35 will be replacing all U.S. F-16s by the late 2020s. That means the U.S. will have plenty of little-used F-16s sitting around, and many allies in need of low-cost jet fighters. Many current F-16 users planned to replace the F-16 with the F-35 but that aircraft costs more than twice as much as a new F-16V so air forces are seeking to operate a mixed force of F-35s and late model F-16s.

Since the 1990s most F-16s produced were for export and these, like the Israeli F-16I, cost as much as $70 million each. Some nations, like South Korea, built over a hundred F-16s under license. The 16-ton F-16 also has an admirable combat record and is very popular with pilots. It has been successful at ground support as well. When equipped with 4-6 smart bombs it is an effective bomber. Since first entering service some 4,600 F-16s have flown over 12 million hours. Despite fears that a single-engine fighter would be less safe, F-16s have, in the 21st century suffered a remarkably low accident rate (loss or major damage) of 2.4 per 100,000 flight hours.

The F-16 is one of the most modified jet fighters in service. While most are still called the F-16C, there are actually seven major mods, identified by block number (32, 40, 42, 50, 52, 60, 70 and 72), plus the Israeli F-16I, which is a major modification of the Block 52. The F-16D is a two-seat trainer version of F-16Cs. The various block mods included a large variety of new components (five engines, four sets of avionics, five generations of electronic warfare gear, five radars and many other mechanical, software, cockpit and electrical mods.)

Until the Block 70 came along, the most advanced F-16 was the F-16 Block 60. The best example of this is a special version of the Block 60 developed for the UAE (United Arab Emirates). The UAE bought 80 "Desert Falcons" (the F-16E) which is optimized for air combat. It is a 22 ton aircraft based on the Block 52 model (which the KF-16 was originally), but with an AESA radar and lots of other additional goodies. The Block 70 goes beyond the Block 60, especially in terms of electronics and airframe enhancement to extend flight life.

The most successful F-16 user is Israel which set a number of combat records with its F-16s. Israel plans to keep some of its late-model F-16s flying for over a decade more as it retires the oldest ones. At the end of 2016, Israel retired the last of its 125 F-16A fighters. The first 70 were acquired in 1980 and 1981 and included 8 two-seater F-16B trainers. One of the F-16As achieved a record by being the single F-16 with the most air-to-air kills (6.5), all achieved in 1982 using three different pilots. Israel received 50 used F-16As in 1994 (including 14 B models) and used these mainly as trainers.

These F-16As were the first of the nearly 400 F-16s Israel obtained from the United States since 1980. Israeli F-16s have shot down 47 aircraft (70 percent of the 67 kills for all F-16s built). Israeli F-16As flew 474,000 sorties and spent over 335,000 hours in the air over 35 years. Israel was the most energetic user of the F-16 and also took the lead in developing upgrades and accessories. This could help selling the older F-16As, but that is a crowded market with more and more of these oldest F-16s being retired rather than upgraded. That is easier to do with the later F-16C models and that what Israel did with all of its F-16Cs.




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