Ask Captain Lim ~ All about Aviation

Hi Captain Lim,

(1) I heard that ETOPS rules are getting changed... something like twin jets ought to be considered as 4-engine jets, etc. Has it affected Boeing 777 operations?

(2) Regarding the incident on the Airbus 300 that crashed at New York where one of the
engines separated from the wing. As far as I know, only engine out is practiced in simulator before V1 and at V2. So how this is taken care of if it happens to a Boeing 777? Is this scenario also practiced in the simulator?

Is the "TAC" (Thrust Asymmetric Compensator) designed to take this into consideration?

Was this metal fatigue defect not detectable in the walk around pre-flight checks? I used to see pilot walk around the aircraft checking control surfaces, landing gear, etc. I never saw a pilot looking at the joints which connect engine and the wing. Sometimes a wing may also break, not because the wing do not have sufficient strength to hold the stresses but because of loose joints.

Thanks and warmest regards,

Srihari J

Hi Srihari,

(1) The latest update on ETOPS points to changes requiring 4-engines airplanes to adopt 2-engines practices rather than vice versa. Below is a summary extracted from the Boeing Infoline site.

On 16.12.02, ARAC, the Aviation Rulemaking Advisory Committee, the advisory committee of FAA, came up with findings and recommendations for ETOPS. It
recommends that ETOPS requirements should not only apply to two-engines but to 3-or-4 engines airplanes as well. Their rationale for this was, to raise the aviation industry to a higher and uniform standard. They have recognized the high safety level already achieved by ETOPS during the last 20 years.

In the past, the initial assumption was that 2 engines were inherently less safe when compared to 3-or-4 engines airplanes. Today, 125 operators flew a total of about 1,100 ETOPS flights every 24 hours. The philosophy of ETOPS ensures the imposition of strict requirements in airplane engine design, increased maintenance practices and reliable backup systems. Hence, we see the robustness and reliability of engines being developed to achieve these enhanced safety standards. It also requires additional measures to protect airplanes, passengers and crew should a diversion arise. The effect of these requirements means that the entire aviation industry have benefited from this philosophy.

Modern jet engines are 50 times more reliable than piston engines that inspired the 60-minutes Rule in 1953. This Rule bars DC-3 from flying extended routes that were better served by 4-engines DC-4. So engine reliability were no longer the single focus of safety concern and this gradually made the Rule obsolete. In 1985, ETOPS came up with a 120 minutes diversion authority, that is, there should not be more that 5 IFSDs (in-flight shut downs) in every 1,000 engines hours. In 1988, the 180 minute authority requires a new figure of not more than 2 IFSDs per 1000 engine hours.

In fact, today, the average IFSD rate is only 1 in 1000. So, engine reliability is no longer a concern. Instead, the Committee argues that other factors are more relevant to overall safety. They are factors such as, cargo fire suppression capability, weather conditions and facilities at the alternate airports. So there should be an uniform standard for all and not just confined to two-engines airplanes. Diversions affect all types of airplanes. They are usually either due to illness of passengers, smoke in
flight deck or cabin, turbulences or adverse weather, fuel leak, cargo fire, IFSD or engine failure.

The proposed regulations changes by ARAC include more reliable voice communications for all airplanes for extended operations. Airplane dispatched on extended flights should be installed with more reliable communication technology. For diversion requirements, pilots should now consider factors such as airplane condition and system status, weather conditions en route, terrain and facilities at the alternate airports. All airplanes on extended operations shall carry fuel reserve for low altitude diversions following an emergency depressurization. Maintenance standards for current ETOPS operators should be applicable to all airplanes for extended operations. Passengers recovery plans should also consider the well being of passengers and crew at diversion airports. Currently, these rules are only applicable to Polar operations only. Cargo fire suppression facilities and all performance data should be available to all extended
operations Polar operations, as recommended to North and South Polar regions should be designated as ETOPS applicability. Rescue and fire fighting requirements at enroute alternate airports should be specified as well.

These are some of the proposals. The FAA will evaluate these ARAC-proposed regulations and is expected to enact these new ETOPS rules, perhaps in late 2004. These new rules would certainly enhance the safety and reliability of all extended operations in all airplanes in the future.

(2) Engine out are practiced between V1 and V2 and also at other times in flight in the flight simulator. Engine failures or separation from wings are sometimes practiced with the 'TAC' deliberately switched off to make it more difficult for the pilots to handle a crippled airplane.

Pilots do external checks that include the physical external structure of the airplane. Metal fatigue are hard to detect on the engine joints because they are hidden behind metal panels. They are only checked by engineers during stipulated maintenance periods.