Friday, June 21st, 2002

Chinese fighter jets dropping like flies
By Brian Hsu
STAFF REPORTER
Four Su-27 fighter planes of the Chinese air force have crashed or have been severely damaged during flight training over the past six months, Taiwanese defense sources said yesterday, attributing the poor performance to human error.

Two of the four planes were damaged while their pilots were trying to land, the sources said. The other two also crashed as a result of human error, they said, without giving further details. It is not known whether any of the pilots were killed.

The accidents bring to 15 the number of Chinese air force Su-27s that have been taken out of service due to crashes. China purchased 46 Su-27s from Russia in the early 1990s.

Of the 31 Su-27s still operational, about 16 are thought to be combat ready at any given time.

The Chinese air force now keeps its best-equipped Su-27s in Guangdong Province, the forward base for the planes.

The rest of the Su-27 fleet, including those that have been damaged, are at a base in Anhui Province.

Over the past six months, the Chinese air force has been trying to enhance the combat-readiness of its Su-27s, despite the lack of trained pilots to fly the advanced planes.

At the end of last year, an Su-27 crashed during large-scale exercises in northern China. The exercise was labeled at the time as a "high-tech drill" by the Chinese military.

It was the only Su-27 crash that year, following several years of incidents involving the accident-prone Su-27s in China.

In the following five months, another three Su-27s, including a twin-seater, developed problems during flight training. One crashed into a mountain, while the other two were badly damaged while landing.

A defense official, who spoke on condition of anonymity, said all these incidents were probably caused by the inexperience and poor training of the pilots.

"Chinese air force Su-27 pilots get only 10 flight hours per month. Practice makes perfect. A lack of sufficient flight training is one of the biggest factors hindering the Chinese air force from leapfrogging [us] in combat strength, despite having advanced fighters such as the Su-27," the official said.

"The Chinese air force purchased a flight simulator for the Su-27. But the single simulator is not adequate for use by all Su-27 trainees and pilots. Sometimes they have to wait months for simulator time," he said.

By contrast, a fighter pilot in Taiwan has much more intensive flight training. Trainees are required to fly 15 hours a month, and sometimes fly as much as 20 hours.

The flight hours do not include the time the pilot has to spend on the flight simulator of the kind of plane he flies, which varies from person to person.

穩定度的定義不是代表平均開機時間而已
而是包含錯誤輸出率的一個指標

穩定度高，系統錯誤率自然低

>
F16就是很典型的4余度電傳系統，而且是沒有機械備份的。
>
否定！在後期型的F-16，其飛控電腦內部為三獨立運算單元，外加一備援單元
為三餘度外加備份系統，且大氣電腦及慣性姿態感測系統僅一套，外加簡易備援單元

備援系統雖然在系統異常時即時接手，但信號非與主系統同時作用
並不計算於餘度內

F-18:
The F-18 incorporated a quadruply-redundant digital fly-by-wire flight control system, the first of its kind to be installed in a production aircraft. It works by having stick and rudder inputs being directed into a computer which interprets them and issues the appropriate commands to the various control surfaces. The FBW system will not allow the pilot to overstress the airframe. The system operates by the principal of majority vote. If one of the four systems disagrees with the other three, this is interpreted as a failure, and the dissenting system is ordered to shut down. FBW redundancy is such that should a second system fail, the remaining two systems can still operate the controls so long as they remain in agreement. In the unlikely event of all four systems failing, there are electrical backups for all control surfaces. There is even a direct mechanical backup for the horizontal tail surface which will give the pilot some degree of pitch control in an extreme emergency.

F-117:
The first prototype flew in early 1978. Naturally unstable, airborne only by virtue of computerized, quadruply-redundant fly-by-wire controls, it exhibited rapid speed loss in nose-up attitudes, a high landing speed and sink rate. This ultimately proved its undoing when Lockheed test pilot Bill Park bounced it off the ground, jamming the right gear halfway up. Unable to land or even belly in, he burned off his excess fuel and ejected from 10,000 feet over the Nevada desert. The prototype was destroyed and Park, injured in the ejection, never flew again.

F-15:
http://www.nieuwkamp.myweb.nl/hist.html

f-16:
Flying Controls
Four-channel digital fly-by-wire (analogue in earlier variants); pitch/lateral control by pivoting monobloc tailerons and wing-mounted flaperons; maximum rate of flaperon movement 52º/s; automatic wing leading-edge manoeuvring flaps programmed for Mach number and angle of attack; flaperons and tailerons interchangeable left and right; sidestick control column with force feel replacing almost all stick movement.

http://idex.janes.com/landforces_data/f16details06.shtml