Dropping Engines

So a Boeing 737-200 (ZS-OEZ for those of you that care about such things) lost an engine today and when I say lost an engine I mean that it fell off!

(Yunus Mohamed, Die Burger)

Here's the airplane back on the ground being prepared for a tow off the runway.


(Yunus Mohamed, Die Burger)

Here's the engine laying in the grass.

Apparently the engine ingested an object of some sort and in turn caused the engine to seize. Of course this has caused all manner of excitement among the media. Well guess what? Aircraft engines are supposed to fall off when an engine suffers a catastrophic failure of this kind. The engine mount is designed this way to prevent damage to the much more important structure just above the engine. What's that structure you ask? Why it's the wing. Why is the wing more important than the engine? Simple an airplane can fly without an engine but it doesn't do well without a wing. Need proof? Check this out.

See that? No engines.

So everyone just relax and don't panic!

Incidentally, this is not the first time that a 737-200 has dropped an engine and safely returned to the ground. I'll post other examples below.

Delta B737-200 7Jan92 DFW Engine separation on takeoff. After T/O at 200' breakaway safety bolts called "Cone Pins" sheared for right engine. Engine bounced on grass on right side of runway.

... FTW92IA055 ....
... DELTA AIR LINES ...
... Tuesday, January 07, 1992 in DFW ...
... BOEING 737-232 ... N322DL ...

THE RIGHT ENGINE SEPARATED ... CLIMBING THROUGH 200 FEET AFTER TAKEOFF. ... UNEVENTFUL LANDING ...

ENGINE SEPARATION WAS THE RESULT OF THE FAILURE OF THE AFT CONE BOLT AND THE ENGINE SECONDARY SUPPORT ASSEMBLY. THE AFT CONE BOLT FAILED AS RESULT OF A PREEXISTING FATIGUE CRACK, WHILE THE ENGINE SECONDARY SUPPORT ASSEMBLY FAILED AS RESULT OF THE DYNAMIC LOADS THAT EXCEEDED THE DESIGNED CAPACITY OF THE MOUNTING BOLTS.

THE TWO FORWARD CONE BOLTS FAILED AT IN OVERLOAD AS THE ENGINE SWUNG FORWARD DURING THE SEPARATION SEQUENCE.

METALLURGICAL TESTING REVEALED THAT THE FATIGUE OF THE AFT CONE BOLT WAS A RESULT OF LUBRICANT INADVERTENTLY INTRODUCED INTO THE CONICAL SURFACE OF THE CONE BOLT.

...Board determines the probable cause ...
THE FAILURE OF THE AFT CONE BOLT AS RESULT OF PREEXISTING FATIGUE CRACKING DUE TO IMPROPER MAINTENANCE, AND THE FAILURE OF THE SECONDARY SUPPORT STRUCTURE AS A RESULT OF LOADS THAT EXCEEDED THE CAPACITY OF THE ATTACHING HARDWARE AND THE CRUSHABLE HONEYCOMB CORE.

---

Piedmont Airlines B737-200, 20Jan89, right engine separated from aircraft after T/O at Chicago. Newly designed secondary support structure had not yet been installed.

... CHI89MA046 ....
... PIEDMONT AIRLINES
... Friday, January 20, 1989 in CHICAGO, IL ...
... BOEING 737-201 ... N242US ...

AN IN-FLIGHT TEARAWAY OF THE RIGHT ENGINE (FROM THE RIGHT WING) OCCURRED AS THE AIRPLANE LIFTED OFF FROM THE RUNWAY. ... CONTINUED THE TAKEOFF ... RETURNED ...

AN EXAM OF ITS WING & SEPARATED ENGINE REVEALED THE AFT CONE (ENG MOUNTING) BOLT HAD FAILED FROM FATIGUE, THEN THE TWO FORWARD CONE BOLTS FAILED FROM DUCTILE OVERSTRESS.

A RAISED MECHANICAL DEFORMATIVE WAS FOUND ON THE CONICAL SURFACE OF THE AFT BOLT. THE DEFORMITY WAS INDICATIVE OF DAMAGE PRODUCED PRIOR TO OR DURING ASSEMBLY OF THE CONE BOLT AT IN THE ISOLATION MOUNT. A MATCHING CAVITY WAS NOTED ON THE ISOLATION MOUNT. THERE WAS EVIDENCE THAT THE MECHANICAL IRREGULARITY RESULTED AT IN A NONUNIFORM FIT WHICH ALLOWED THE TORQUED FITTING TO LOOSEN DURING CYCLIC LOADING.

AD 88-01-07 REQUIRED THAT ULTRASONIC INSPECTION OF THE CONE BOLTS BE PERFORMED AT INTERVALS NOT TO EXCEED 600 CYCLES. AN ULTRASONIC INSPECTION OF THE BOLTS HAD BEEN ACCOMPLISHED ABOUT 330 CYCLES BEFORE THE ENGINE SEPARATED.

... Board determines the probable cause ...
PREVIOUS DAMAGE TO THE AFT CONE (ENGINE MOUNTING) BOLT, WHICH RESULTED AT IN MISMATCHED SURFACES BETWEEN THE BOLT AND ISOLATION MOUNT, LOSS OF TORQUE DURING CYCLIC LOADING OF THE MOUNTING BOLT, AND SUBSEQUENT FATIGUE FAILURE OF THE BOLT.

---

US Air B737-200 PHL 5Dec87 #2 engine separated shortly after takeoff. Cracks caused by metal fatigue in one of three bolts; after rear bolt failed the two forward bolts and support cable failed in overload.

... NYC88FA050 ....
... USAIR
... Saturday, December 05, 1987 ... DEPTFORD, NJ ...
... BOEING 737-2B7 ... N319AU ...

DRG TKOF, AS USAIR FLT 224 WAS CLBG THRU 4000', THE ACFT YAWED/ROLLED RGT. SIMULTANEOUSLY, THE CREW NOTICED THE #2 THROTTLE SLAM/LOCK TO THE IDLE PSN & A CONTINUOUS AIRFRAME BUFFET BEGAN.

SOON THEREAFTER, THE #2 ENG SEPD FM THE ACFT & THE BUFFET STOPPED.

THE ENG IMPACTED IN AN OPEN FLD, 6 MI FM THE ARPT.

JUST BFR AND IT SEPD, A PAX SAW THE AFT END OF THE #2 ENG MOMENTARILY DROOP ABOUT 30 DEG.

AFTER ENG SEPN, THE 'B' HYD SYS LOST PRES & THE TE FLAPS WOULD ONLY EXTD 10 DEG.

THE ACFT WAS LNDD SAFELY AFTER AN EMERG GEAR EXTN & DIFFERENTIAL BRAKING WAS USED FOR STEERING.

AN EXAM REVEALED THE AFT MOUNT CONE BOLT FOR THE #2 ENG HAD FAILED FM FATIGUE THRU THE THREAD RELIEF UNDERCUT RADIUS. FATIGUE CRACKS HAD INITIATED ON DIAMETRICALLY OPPOSITE SIDES OF THE RADIUS. SUBSEQUENTLY, THE FWD MOUNT CONE BOLTS & SECONDARY SUPPORT CABLE FAILED FROM OVERLOAD.

... Board determines the probable cause ...
ENGINE INSTALLATION, MOUNTING BOLT ..FATIGUE

---

Southwest 223/3Jan86 B737-2H4, after T/O from Love Field (Dallas), Rt Engine rear mount Cone Bolt sheared, mount failed and restraining cable broke; leaving the engine attached by only the two fwd mount bolts; returned safely. [AWST 124:31 Ja 13'86, photo.]

... FTW86MA030
... SOUTHWEST ...
... January 03, 1986 in DALLAS, TX
... BOEING 737-2H4 ... N86SW ...

THIS INCIDENT OCCURRED WHEN THE NO. 2 ENGINE EXPERIENCED AN AFT ENGINE MOUNT CONE BOLT FAILURE AND THE SUBSEQUENT FAILURE OF THE SECONDARY SUPPORT LINK (STAINLESS STEEL CABLE).

THE FAILURE OF BOTH AFT ENGINE SUPPORT ASSEMBLIES DURING THE TAKEOFF ROLL ALLOWED THE AFT SECTION OF THE ENG TO HANG DOWN TO WITHIN 4' [sic, transcription err] OF THE GROUND. AS A RESULT, THE NO.2 THRUST REVERSER ACTUATOR ASSEMBLY DRUG THE RUNWAY ON ROTATION.
... RETURNED ... LANDED...

METALLURGICAL EXAMINATION OF THE CONE BOLT REVEALED THAT AND IT FAILED AS A RESULT OF FATIGUE, MOST PROBABLY DUE TO IMPROPER INSTALLATION OF THE BOLT, SPECIFICALLY, THAT AND IT WAS UNDER TORQUED WHEN THE OPERATOR RE-INSTALLED THE ENG.

THE SAFETY CABLE FAILED AS A RESULT OF OVERSTRESS, PROBABLY INDUCED WHEN THE ACFT ENCOUNTERED A ROUGH STRETCH OF RUNWAY DURING THE TAKEOFF ROLL.

... Board determines the probable cause ...
ENGINE INSTALLATION, SUSPENSION MOUNTS .. FAILURE, PARTIAL
... FATIGUE ... SEPARATION ... OVERLOAD ... UNDERTORQUED
MAINTENANCE, INSTALLATION .. IMPROPER ...

Contributing Factors ... RUNWAY / LANDING AREA CONDITION ... ROUGH /UNEVEN

Missing wing tip causes passenger revolt

11/04/07 The Daily Mail said Saturday that seven SriLankan Airlines customers
demanded they be allowed to exit the aircraft while it was at the British
airport after they learned it was missing a 5-foot wing tip.

Why do people think that the crew of an airplane would put themselves at risk? What possible motive could they have do something like this? Could it possibly be that the flight crew knows more about flying then the passengers? Can it be that flying an airplane with missing parts is possible and maybe even safe?

















Here's a fine example of just such a thing.

But back to the original story of a missing wingtip. There exists in the world of aircraft a document known as the Configuration Deviation List (CDL). This approved document lists those items of the aircraft that can be missing. The following is a quote from the CDL for the A320. (I don't have access to an A340 CDL but suspect that it is very similar to this one)

One complete wing tip fence may be missing provided:
a) Exposed interior structure is covered with high speed tape,
b) The following performance penalties are observed:
1) Takeoff and approach climb limiting weight is reduced by 4%.
2) Fuel consumption is increased by 1.4%.
c) Wing tip fence is replaced at the earliest maintenance opportunity and mean while, protective material must be inspected before every flight and replaced if necessary, and
d) The one engine inoperative net ceiling is reduced by 300 feet.

As you can see, by making a few allowances in performance calculations, it's perfectly normal and safe to fly the airplane with a missing wingtip.

One other thing...

This picture is floating about the internet allegedly showing the damage to the A-340's wingtip, there's just one problem. The circled items in this picture belong to the British Airways 747 in the background.

So please, everyone relax and don't panic!