"Hard Landing" in Venezuela

[grizzled]

Or so the headline says. Yup; I'd say when the engines are left swinging in the breeze and the fuselage is buckled, you could call it a hard landing... ;)

Accident: Aeropostal DC95 at Puerto Ordaz on Sep 26th 2011, hard landing tears engines off (http://avherald.com/h?article=4438e8ff&opt=0)

[kms901]

AT least the whole tail didn't fall off this time !

[Sir George Cayley]

Anyone seen the pax in 24B's dentures?

[kms901]

Probably in the pax in 23b's backside !

[dixi188]

Would that be shear pins breaking to cause the pylons to come adrift.
Are they lifed like the B747?

[VFD]

Would that be shear pins breaking to cause the pylons to come adrift.
Are they lifed like the B747?
Since from the picture, the fuselage being seriously buckled we can pretty much assume that we did not have shear pin failure on two engines.

I know that the engines are mounted with fuse pins, I just wonder how many "G's" it takes to make them shear?
Second question was the G loading enough to partially colapse the seats.
I am sitting here with a sore back just looking at the G loads.

[Carbon Bootprint]

Second question was the G loading enough to partially colapse the seats.Good question. How many Gs does it take to buckle the crap out of the rear fuse like that? :confused:

[DownIn3Green]

Don't quote me, but if the shear pins "sheared", it would be from the pylons, not the fuselage...

[lilflyboy262]

Is that the reversers open on the right hand engine?
Force hard enough to open them? One opened prematurely?
Would turn the plane the flight characteristics into a crowbar if it did.

[lomapaseo]

Agree that the buckled fuselage is a pointer to the over-G hard landing.

The DC9 shear pins are quite a bit different than the mounting pins in the B737 and B727 (diiferent load paths etc.).

There have been cases where after-market work installing hush-kits etc, has mistakenly swapped Boeing fuse pins into Douglas aircraft. Aint nobody broke one that I know of.

[KingChango]

Not everyone can tame the beast:D

[Escape Path]

Force hard enough to open them? One opened prematurely?
Would turn the plane the flight characteristics into a crowbar if it did.

No such capability on the DieSel 9. Probably a side effect from the hard landing.

[lilflyboy262]

As in don't have the capability for thrust reversers? Or the capability for it to deploy in flight?

Because the -50 model certainly has thrust reversers. As for the capability for it to deploy in flight... well if its mechanical, it can fail.

The reason why I think it has deployed in flight is that after the landing and the engines have seperated to the extent that it has, one would think that the engines controls would no longer work.

Just my take on things. More than happy to be proved wrong and learn something new!

[grizzled]

Re thrust reversers...

The latest photos (on the same link above) show the starboard reverser deployed and the port reverser stowed.

[Mad (Flt) Scientist]

The reason why I think it has deployed in flight is that after the landing and the engines have seperated to the extent that it has, one would think that the engines controls would no longer work.

Depending on the nature of the control and the sequence of the failure, I can conceive of a mechanical control to the TR (which I suspect an aircraft of this vintage might have, rather than electrical) remaining connected (briefly) as the engine started to detach. If that resulted in a "cable pull" in the correct sense, it might be enough to get the TRs deployed (or at least unlocked, so that residual thrust caused the deployment to complete).

Speculation, but once the anchor points for a mechanical system start to move relative to each other, unusual behaviour is possible.

[Escape Path]

@lilflyboy262

I meant capability to deploy the TR's in flight. Since it is a mechanical function, it surely can fail, however, I can't think of a reason why only one TR would deploy when the engine is coming from a rather constant mode of operation (approach and landing) and if it did deployed in flight, I think we would be looking for either more serious damage (emphasized on the side with the reverser opened) or no damage at all if the height the reverser deployed at was low enough (which we cannot tell at all with the information we have now).

My 2c is that it is a consequence of the hard landing, since if I recall correctly, the reverser clamshells on the -9 series are mechanically held close by a or a series of pins. If those pins sheared because of the force of the landing I think that sort of damage could happen.

I stand to be corrected though...

[pigboat]

Bet all the ladies were wearing fur collars after that one! :eek:

[grounded27]

I know that the engines are mounted with fuse pins, I just wonder how many "G's" it takes to make them shear?
Second question was the G loading enough to partially colapse the seats.
I am sitting here with a sore back just looking at the G loads.

Yeah, I call BS on no injury's reported, they may have walked off but will be paying the piper in the AM!

[Volume]

Would that be shear pins breaking to cause the pylons to come adriftThere are no shear pins designed as fuse for rear mounted engines. They are designed to protect the wing structure and its integral fuel tanks from rupture, not required for fuselage mounted engines.

[andrasz]

...Probably a side effect from the hard landing...

Why not intentional... ? We do not know the exact sequence of what happened here, it is concievable that after landing the T/Rs were deployed ormally, after all the pilots had no idea what was going on back there. Possibly on the right engine the controls were not severed, or the engine support failed in steps allowing a brief time for T/R deployment.

[grounded27]

after all the pilots had no idea what was going on back there. Possibly on the right engine the controls were not severed, or the engine support failed in steps allowing a brief time for T/R deployment.

Quite sure all cables and hyd lines were broken at this point (of picture)

[Tourist]

Aircraft lands heavy.
Left engine rips off immediately, right is damaged.
Pilots unaware select reverse thrust.
Weakened right engine is ripped off by reverse thrust.

Maybe?

[andrasz]

Quite sure all cables and hyd lines were broken at this point (of picture)

No question about that.

If you look at the video of the test flight hard landing, you can clearly see a flex oscillation cycle before the tail separates. If something similar happened here, that would have allowed for the second or two needed for a commanded T/R deployment, assuming it was done so immediately after touchdown. Not saying this is what happened, just raising the possibility.

[lomapaseo]

Quite sure all cables and hyd lines were broken at this point (of picture)

Then what is keeping the engine still on the aircraft:confused:

[lomapaseo]

There are no shear pins designed as fuse for rear mounted engines. They are designed to protect the wing structure and its integral fuel tanks from rupture, not required for fuselage mounted engines.

Almost 100% correct :ok:

Everything in the load chain has a designed limit (shear pin). Some greater than others. Start with the engines and apply a pin strength greater than most engine failure conditions. Than move onto more critical stuff like pylons, fuel tanks, wings (do we care about tails?) and make sure that your normal design limits (like gust loadings, landing etc.) are stronger.

The assumption in this case is that the mount pins on the DC9 are weaker than the mount pins for the same engine on the B737.

That leaves the question about the rear engines on the B727 vs the DC9. I believe you will find that the shear pins on the B727 are hollow just like the B737, while the pins on the DC9 are solid. Obviously both are designed to protect the aircraft and to do this they can set their strength anywhere between regulated aircraft design conditions and regulated engine design conditions. The anywhere in between is up to the manufacturer

[lakerman]

If you look at the photographs carefully you will see both engines are still attached to their respective pylons. The engines are hanging down because the skin/rear fuse structure has torn off, thus allowing the engines to hang down, but still on the substructure/ stub wing.

[AN2 Driver]

Not the first time this happens. I remember a Scandinavian DC9 (SE-DAT if memory serves right) at Trondheim in 87 which ended up in a similar state, yet they actually went around :eek: and did what proved to be the last ever circuit and landing of that airplane...... yet all on board made it safely out on probably quite shaky legs.

I remember that Flight at the time called it the "flight of a bumble bee" because it was not supposed to fly in this condition but did it anyway.

[Escape Path]

Could there be an indication via the engine instruments that something very very very wrong has happened to the engines? Something like instrument needles off their scales or severe fluctuation? Anything in the cockpit alerting the crew of an engine separation?

[Aviaservice]

I guess the niddles were pulled in by their axels.

[500N]

"Anything in the cockpit alerting the crew of an engine separation?"

A complete loss of thrust ??????

.

[Dreamflyer1000]

no vibration indications? Im sure if the engines were still running at this point, they would be making a fair amount of abnormal noise and vibration!

[Escape Path]

A complete loss of thrust ??????

That doesn't necessarily means an engine separation...

[golfyankeesierra]

"Anything in the cockpit alerting the crew of an engine separation?"

A complete loss of thrust ??????

During touchdown thrust is idle anyway..

Wonder what the hydraulics did; loss of all fluid or are there protections?
Not so nice to lose nose wheel steering and brakes at the same time!

[Shrike200]

In a relatively recent B737-200 engine separation, the only noticeable difference between that and failure was the engine indications flagged themselves (ie didn't just run down to zero/windmill RPM), and the thrust lever got forcibly pulled to idle due to the cable being pulled. AFAIK. Not that one would immediately put all that together in the heat of the moment....if it indeed happened here.

[IGh]

Here's some historic ARC-damage mishaps for DC9 --

Overseas National / 3May69 DC9 N934F, military cargo, hard landing & bounced, Keel Extrusion fracture, wrinkled skin.

EAL DC9-31 N8961E FLL 18May72, heavy rain with TRW; hard landing, fracture of aft fuselage and tail separation. [See DC-9 mid-fuselage fractures of 26Mar92, 30Mar92, and 27Dec87; and bent eng mts of Feb'87; and T-tail separation of 2May80.]

DC-9 Super 80 [MD80] N980DC #1 test ship 2May80 hard landing accident during flight test; Edwards AFB California.

Garuda / 11Jun84 DC9-30 Reg PK-GNI Jakarta, Indonesia; hard landing, severe structural damage.

25Feb87 SAS DC9-41 SE-DAT hard landing at Trondheim; bounced & G/A. Engine mounts deformed, Fuselage cracked. [Flt Int'l]

Eastern / 27Dec87 DC9-31 N9848E at 11:39pm, hard landing at Pensacola Regional Airport, split fuselage section. … After first touchdown aircraft bounced forty feet, then on second touchdown fuselage broke open just aft of wing root; and impact drove the nose LG into fuselage (no tires burst). Circumferential split (see AW photo), aft section of fuselage dragged along runway. [AW 128:68-9 Ja 4 '88]

Intercontinental de Aviacion / 26Mar92 DC9-15 HK-2864X hard landing Tumaco, Columbia: Fuselage cracked near Wing T.E.

Aviaco / 30Mar92 DC9-32 EC-BYH hard landing at Granada Spain; fuselage broke off aft of Wing T.E.

ValueJet / 7Jan96 DC9-32 N922VV hard landing at Nashville: on final approach to Rwy 2R Ground Spoilers deployed while still airborne; high sink rate; touchdown short of threshold; substantial damage to aft fuselage, empennage, flaps, slats, and both engines. // NTSB rec’md FAA req’ airlines review cold-weather nosegear servicing … Cold T/O from ATL, NLG strut failed to extend (no air/grnd shift): preventing LG retraction and cabin pressurization. Checklist instructed pilots to open the Grnd Cntrl Relay C/B; flt continued to BNA. Grnd Spoilers deployed when C/B was reset while still airborne. \\ AW&ST, Jul 1’96, pg31; Dec 16’96, pg 30.