Seaplane down

[N9IWP]

http://www.aero-news.net/news/commai...4e15&Dynamic=1

A Grumman Mallard (one of my favorite planes) operted by Chalks Ocean Airways has crashed. It is beleived all aboard (2 crew, 17 passengers) have died .

Being a seaplane pilot is one of my "dream jobs" - something I think about but am unlikely to do anything about.

Chaulks is arguably the oldest US commercial airline, founded in 1919. This is thier 1st passenger deaths (in 1994 a pilot and co-pilot died)

Brian

[Johnny L.A.]

Been watching the coverage on CNN. Well, not watching watching. But it's been on. Seems they haven't gotten the experts they had for other aviation (i.e. 'plane in trouble') stories.

Looked like a wing exploded?

[Johnny L.A.]

New video. It looks like the starboard wing departed the aircraft, and was on fire.

[Robot Arm]

Originally Posted by N9IWP

Being a seaplane pilot is one of my "dream jobs" - something I think about but am unlikely to do anything about.

I did a college internship at a company that builds floats and reconditions old DeHavilland Beavers. There's a lot to know to fly off the water, but it's fascinating stuff.

[Shagnasty]

Let's see,

Plane catches fire and may have broken up before crashing and killing all aboard.

It was a seaplane, one of the few commercial planes that doesn't take off from an airport. The relative lack of formality and security was what makes planes like that appealing to some.

Christmas is just around the corner.

[N9IWP]

If the plane had headed towards downtown Miami maybe, but 20 people seems an awfully small target.

Brian

[Richard Pearse]

Originally Posted by Shagnasty

Let's see,

Plane catches fire and may have broken up before crashing and killing all aboard.

It was a seaplane, one of the few commercial planes that doesn't take off from an airport. The relative lack of formality and security was what makes planes like that appealing to some.

Christmas is just around the corner.

Uncontrolled engine fire burning through the wing would be a more likely scenario.

[Johnny L.A.]

Originally Posted by 1920s Style "Death Ray"

Uncontrolled engine fire burning through the wing would be a more likely scenario.

I agree that a problem with the aircraft is more likely than an intentional downing.

Question: What is the engine-fire record of the Pratt & Whitney PT6?

Okay, I think we all have our ratings here. Right? So you'll understand if I do a bit of amateur post-crash analysis (with the caveat that we don't know anything until the NTSB report comes out).

The smoke trail seemed fairly short. In my non-professional opinion I would guess that the aircraft suffered a sudden, catastrophic failure. If there had been a slow fire, I think one of the passengers (who were probably looking out the windows -- I know I do) would have noticed something. I think the pilot may have had time to make an emergency landing. (Is it still 'ditching' in a seaplane?) But the short smoke trail and the seemingly immediate nature of the steep dive indicate, to me, a non-professional, that the failure was sudden. i.e., I'm guessing there was an explosion.

What would cause an explosion? Obviously a bomb would. Only as Ray points out, it's a pretty poor target for a terrorist considering other available targets. Jet fuel is less volatile than avgas (lower 'octane', as it were -- although kerosene doesn't use 'octane') but as was seen in TWA Flight 800 its vapours are capable of an explosion under the right conditions. Why would Jet-A explode? An electrical fault, as in TWA 800? Maybe.

Or a catastrophic failure of the engine might cause a turbine blade to puncture the fuel cell. If that fuel sprayed onto the hot engine, I believe the result would be explosive. Which brings me back to the question of the P&W PT6. I have not made any studies, nor even casual observation of failures of these engines. AFAIK they are one of the most reliable powerplants in the industry. I personally have not heard of even one of them flying apart. I just don't have the data.

I'm guessing that the fuel cell was punctured in some way, possibly by a turbine blade, causing fuel to spray on the hot engine causing a fast fire/explosion that severed the starboard wing.

I am not a crash investigator. The only data I have is the video I saw on the news. We really won't know anything until the official investigation has been completed and the NTSB releases its report -- which tends to take a rather long time. But that's my non-professional theory.

[ElvisL1ves]

The G73T seems to have the engines entirely forward of the wing. The PT6 isn't all that long, being a reverse-flow design, and the hot section is up front anyway. A hot-section failure would involve the fuselage, not the wing, except for secondary damage from perhaps a severed fuel line.

This happened right after takeoff, for another thing, so a liquid-fuel-initiated fire doesn't seem like it would have enough time to act. I'd vote for a fuel-vapor explosion as my top suspect. I've read elsewhere (can't put my finger on it) that Chalk's had a plane hijacked to Cuba once, and ever since their policy has been to never have enough fuel on board to get there (and it's only a little farther than their normal south-Florida-Bahamas routes). That leaves a helluva lot of empty space in the tanks for fuel vapor to collect.

Just guessing, like everyone else, though.

[Johnny L.A.]

Your theory sounds better than mine.

Only I can't help thinking of the thousands of turbine-powered aircraft that fly with partial tanks. The only other aircraft I can think of whose vapour-filled fuel cell exploded was TWA 800, mentioned earlier. (Not to say it hasn't happened to other aircraft, just that that's the only one I can think of. Oh, wait. There was Apollo 13, after a fashion.) What could have caused the spark, if that indeed was the cause? The Grumman was an old aircraft, but the turbines are a more-or-less 'modern' upgrade. Being a relatively small aircraft, I would think that frayed wiring would have been spotted in the 100-hour or Annual inspections. OTOH, seaplanes operate in a fairly harsh environment. I've never flown a float plane, but I have the impression that the take-offs and landings -- especially in open water -- may be a bit bouncy. Severe vibrations or shocks can cause damage that may go unnoticed between inspections.

Does anyone (N91WP?) know the Mallard well enough to know what may have ignited fuel vapours, how the wiring goes, etc?

[ElvisL1ves]

More.. There have been 2 737's destroyed by center-tank explosions, one in Manila, one in Bangkok. I've seen references to a KC-135 having it happen in England, too. Other incidents that hadn't, or couldn't, have their causes determined might be added to the list.

[N9IWP]

Sorry, don't know anything about the fuel / electrical system of the Mallard.

Brian

[Terminus Est]

Video on CNN shows the seaplane falling into the water with the fuselage, tail, and at least one wing and engine intact. This was closely followed by flaming wreckage of what appears to be other wing and engine.

[Anne Elk]

Paul Harvey, radio guy and amateur NTSB investigator, announced that he suspected metal fatigue, then said that the real investigation will not be finished for several months. I think I'll wait for the feds to find out what caused the crash. For now, I will grieve for the 20 lives lost.

[Rick]

Before I looked at any fuel tank explosions, I would be more worried about structural failure. Remember the Aloha Airlines 737 with a sunroof?
Seaplanes live in a very hostile corrosive environment. Salt water eats aluminum. Little bit of corrosion on this spar, that spar, and before you know it the wing fails. When the wing fails, fuel leaks, sparks fly, fire starts.

[Larry Mudd]

I was watching CNN when this happened, and noticed that for the first fifteen or twenty minutes, they kept talking about a "hydroplane" that had crashed -- then they switched over to "seaplane" without comment.

Very confusing. It didn't help much that they also had a guy from the Coast Guard on the phone and kept asking questions of him even though he clearly said that the only source of information he had at the time was the TV he was watching, tuned to CNN. "What can you tell us about the weather?" "Well, I'm nowhere near the scene, but from what I can see on the TV, it looks pretty clear." Aye-yah.

[Johnny L.A.]

Originally Posted by Rick

Before I looked at any fuel tank explosions, I would be more worried about structural failure. Remember the Aloha Airlines 737 with a sunroof?
Seaplanes live in a very hostile corrosive environment. Salt water eats aluminum. Little bit of corrosion on this spar, that spar, and before you know it the wing fails. When the wing fails, fuel leaks, sparks fly, fire starts.

Possibly, only AFAIK Mallards aren't pressurised. Many pressurisation cycles is a contributing factor in metal fatigue. But yeah, spars have been known to fail through corrosion.

[Scruloose]

That really sucks. My thoughts are with those families.

Being stationed at the CG base there twice, I've watched that plane land and take off in the cut hundreds of times (and dodged it a few times as well). I was always amazed how they operated in one of the busiest waterways in the US as the least privileged 'vessel' on the water without any mishaps.

I suppose one small fortunate aspect of this tragedy is that it could have been much worse, given the volume of traffic in that waterway.

[Beware of Doug]

Suppose this crash will be the death knell for the already fast-disappearing flying boat fleet?

[Shagnasty]

Originally Posted by Beware of Doug

Suppose this crash will be the death knell for the already fast-disappearing flying boat fleet?

I don't think so. They are really needed in places like Alaska. Hawaii, and the Caribbean. I go to the USVI fairly often and seaplanes are the best way to take quick trips to other islands. A boat is way too slow for a 50 mile trip and a real airport is too large, time-consuming, and expensive.

[Richard Pearse]

Originally Posted by Rick

Before I looked at any fuel tank explosions, I would be more worried about structural failure. Remember the Aloha Airlines 737 with a sunroof?
Seaplanes live in a very hostile corrosive environment. Salt water eats aluminum. Little bit of corrosion on this spar, that spar, and before you know it the wing fails. When the wing fails, fuel leaks, sparks fly, fire starts.

Yes, I may have looked at it the wrong way.

Anyone remember the C130 fire bomber that had its wings fold up during a pull-up after a bombing run? It also caught fire at the break points before impact.

There is a pearling company here (Paspaley Pearls) that uses Mallards to service the pearl farms, they will be looking at this with interest I would guess.

[Richard Pearse]

There is more discussion of the accident here.

[Rick]

Originally Posted by 1920s Style "Death Ray"

Yes, I may have looked at it the wrong way.

Anyone remember the C130 fire bomber that had its wings fold up during a pull-up after a bombing run? It also caught fire at the break points before impact.

There is a pearling company here (Paspaley Pearls) that uses Mallards to service the pearl farms, they will be looking at this with interest I would guess.

Was it a Hurkey bird? I thought it was a WWII vintage bomber (A26?) I don't have much time now or I would go search. Maybe later

[Richard Pearse]

I was thinking of this one, which is a C130.

[Diceman]

I heard on the news that the plane was 50 years old. Admittedly, I don't know much about aircraft, but that seems pretty old. On the video, it looks like the wing broke off right at the fuselage, or close to it.

I'd put my bet on metal fatigue.

[Johnny L.A.]

Originally Posted by Diceman

I heard on the news that the plane was 50 years old. Admittedly, I don't know much about aircraft, but that seems pretty old. On the video, it looks like the wing broke off right at the fuselage, or close to it.

The average age of the General Aviation fleet (the Cessna, Piper, Beechcraft, et al. you see flying around) is something like 30 or 35 years. Peak production was in the late-1970s, but there were a lot of airplanes made before then. There are a lot of 40 and 50 year old airplanes flying around. The first DC-3 flew 70 years ago, and there are still several in regular service. One operator says that when they can't get the Pratt & Whitney radials rebuilt anymore, they'll just put on turbines.

Aircraft are usually very well maintained. Unlike cars, it is often or usually cost effective to keep them up. When corrosion occurs or fatigue cracks are found, they are repaired. If a problem shows up in the same place in the same type of aircraft, Airworthiness Directives are issued so that the problem can be repaired or avoided in the rest of the type.

Certainly fatigue or corrosion may have been the cause of this crash. But I would have no problem going up in a decades-old aircraft.

[Richard Pearse]

Originally Posted by Diceman

I heard on the news that the plane was 50 years old. Admittedly, I don't know much about aircraft, but that seems pretty old. On the video, it looks like the wing broke off right at the fuselage, or close to it.

I'd put my bet on metal fatigue.

Age could be an issue. Aircraft should have a maintenance schedule that catches and replaces aged items before they become a problem, but it can sometimes take an accident to highlight a particular problem. A good example is that all Tiger Moths now require a check of the wing spar for rotting wood every five years. This requirement was put in place after a Tiger Moth had a structural failure while performing aerobatics.

I would suggest that corrosion would be more likely than metal fatigue, but it could be either I suppose, or something else entirely.

The aircraft that I fly are subjected to a lot of sea spray and they sometimes find corrosion in a wing spar that needs to be repaired.

[GusNSpot]

Malfunction propeller control will do that kind of damage.

Back in the day when the ARMY was first using the Mohawk, there was a rash of crashes that turned out to be propeller control failures and the propellers were going into full reverse pitch at takeoff power settings.

From what I have seen, to knock a Grumman Iron and Foundry works aircraft down, it would usually take something that bad.

Unless there was some CAT or other turbulence at that time, or something that could jerk the controls very violently, well, I personally will wonder about a structural failure due to fatigue or corrosion judging by what folks in the business have said about that operation and the type of care they usually take.

YMMV

[N9IWP]

Probable metal fatigue crack in the wing spar;

"This crack appears to extend through a majority of the spar at the location of the separation," Rosenker said.

http://www.cnn.com/2005/US/12/21/miami.crash/index.html

Brian

[Johnny L.A.]

Originally Posted by N9IWP

Probable metal fatigue crack in the wing spar;

Sounds like Paul Harvey may have been right.

Thanks for the link.

[Beware of Doug]

Originally Posted by Shagnasty

I don't think so. They are really needed in places like Alaska. Hawaii, and the Caribbean. I go to the USVI fairly often and seaplanes are the best way to take quick trips to other islands. A boat is way too slow for a 50 mile trip and a real airport is too large, time-consuming, and expensive.

Floatplanes could fulfill most of these roles, though. I'm thinking of flying boats per se = hull-fuselage craft without floats (eg: Mallard, Albatross, Catalina). They're older, larger, and less economical to run. One good crackup could be the tipping point to relegate them to firefighting duty and warbird meets.

[ElvisL1ves]

Originally Posted by Rick

Was it a Hurkey bird? I thought it was a WWII vintage bomber (A26?)

There were crashes in near-succession of a C-130A (from the Fifties) and a WW2-era Privateer (the Navy B-24) in firefighting duty, both attributable to simple fatigue life. The US Forest Service ordered the grounding of all the old warbird tankers after that (by suspending contracts with their operaators).

Thanks for the update, N9IWP. It makes complete sense. It also pretty much has to mean the grounding (pending re-sparring, a major but doable operation) of the Mallard fleet (and Chalk's), or at least the imposition of a strict inspection schedule.

Trivia: Chalk's is the world's oldest operating airline. The oldest continuously-operating major airline is KLM, however.

[Johnny L.A.]

There are probably more float planes than seaplanes. Up here Beavers and Otters are especially popular, and there is a plethora of float-equipped Cessnas. Seaplanes like the Mallard seem to be more popular in the Caribbean.

As for economy, many of the older aircraft including the accident aircraft have been retrofitted with turbines. Not being turbine qualified (even in helicopters) nor multi-engine rated, I don't know how much more economical they are than radial-engined aircraft. Airplanes are expensive to operate, no matter what engine you use. But it seems to me that if turbines were not cost effective they would not be used in place of radials. (Most of the DeHavillands I see up here still use radials, and I've never seen a Cessna 195 with a turbine.)

[N9IWP]

There aren't many modern flying boats.
http://en.wikipedia.org/wiki/List_of..._and_seaplanes

Ones that are semi recent (not a complete list)
Bombardier CL 415 (water bomber)
Dornier Seawings Seastar (cancelled, seeking investors)
Beriev Be-103 (only new multi-engine flying boat certified in US)
Beriev Be-112 and -200
Seawind 300C (was a kit, trying to become certified)

Pending there is the Centaur (been in development forever- looks like they made a UAV) www.centaurseaplane.com
and the Mermaid http://www.sportaircraftworks.com/mermainmain.html

There are also ultraulight flying boats like the SeaRay

Brian

[N9IWP]

Chaulks has voluntarily grounded its fleet to allow for inspection.

http://www.aero-news.net/news/commai...c22a&Dynamic=1

Brian

[Beware of Doug]

Originally Posted by Johnny L.A.

There are probably more float planes than seaplanes. Up here Beavers and Otters are especially popular, and there is a plethora of float-equipped Cessnas. Seaplanes like the Mallard seem to be more popular in the Caribbean.

I would imagine the flying boat is more suited to warm-water regions, by virtue of the wear and tear on floats vs. fuselage, the ease of repair of floats, and the material stresses of cold weather operations and possible chunks of ice piercing your hull. But The RCAF is still using Albatrosses, last I heard (from a retired USCG pilot who flew them, too). I dunno, really.

[Robot Arm]

Float planes have a little more flexibility where facilities are limited, too. If you're flying to a lake in the middle of nowhere, you can beach the plane, kill the engine and walk to the front of the floats and hop off onto dry land. (Then we'd turn it around and pull it up on the beach as far as we could, and it was ready for when we were leaving.) From the pictures I've seen of the Grummans, it looks like that would be hard to do.

The place I worked was also certificating a right-side door modification for the Cessna 206. When you're docking a float plane, you can't always pick the most convenient approach or even which side of the plane will be at the dock. A stock 206 only has a left-side door for the front seats. With the mod you could approach the dock, cut the engine and get out on the right float as your momentum carried you to the dock.

[Richard Pearse]

All of the float-planes I've seen have been single engine, where as most of the sea-planes have been twins, that would be a compelling reason to have a sea-plane for some companies.

[ElvisL1ves]

My understanding is that all scheduled-passengers-for-hire aircraft in the US have been required to be multi-engined since the 1930's.

[Johnny L.A.]

Originally Posted by 1920s Style "Death Ray"

All of the float-planes I've seen have been single engine, where as most of the sea-planes have been twins...

Link.

[GusNSpot]

Originally Posted by Johnny L.A.

Link.

Exactly the one I thought of also.

My older sister got her Multi-sea rating in on of These..

[Terminus Est]

What's the difference between a float-plane, seaplane, and flying boat?

[Johnny L.A.]

A seaplane is an airplane that is capable of taking off from and landing on water.

A float plane has 'floats' -- i.e., pontoons -- attached in place of the wheeled landing gear. Floats may or may not be aomphibious, i.e. equipped with a retractable undercarriage for use when landing on land.

A flying boat is an airplane with a hull-shaped fuselage instead of floats. Flying boats may or may not be amphibious.

[Robot Arm]

A seaplane is any airplane that can take off and land on the water. A flying boat is a seaplane where the fuselage directly contacts the water, and the airplane is designed from scratch to operate that way. A float plane is a regular, land-based airplane that has had large, external pontoons fitted to it. The Grumman that crashed was a flying boat, the last two links posted in this thread are float planes.

You'll also see some referred to as "amphibious", which means they have retractable wheels and can operate from water or land. And if you're coming in for a water landing, don't have the wheels down; that would be bad.

[JRDelirious]

And down a couple of blocks from where I work I could catch a flight on one of these.

[Robot Arm]

No thread on oddball, twin-engined floatplanes would be complete without this, and this.

[N9IWP]

Pix of the spar crack
http://www.aero-news.net/news/commai...905f&Dynamic=1

Brian

[Richard Pearse]

Originally Posted by Johnny L.A.

Link.

Ja, ok. Obviously just a quirk of where I live that the floats are singles and the flying boats are twins!

Another reason to favour a flying boat over a float plane is that they presumably have less drag and therefore go faster for the amount of fuel used. Some float planes have a heap of drag hanging under them.

[Beware of Doug]

Originally Posted by ElvisL1ves

My understanding is that all scheduled-passengers-for-hire aircraft in the US have been required to be multi-engined since the 1930's.

True. This regulation was put in place in 1934 after some spectacular crashes involving single-engine passenger craft, notably the fast Lockheed Vega family. (Federal favoritism toward the big players in the industry – Boeing, Douglas, and their main customers United and TWA – might also have been a factor.)

[GusNSpot]

A float plane is a regular, land-based airplane that has had large, external pontoons fitted to it.

And their are always exceptions.

Grumman Duck

Some of the 1930's air racers were also pontoon birds.....