NZ8800
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DC4 DC6 DC7 - Balance On Ground

Sun Jul 09, 2006 8:55 pm

The DC4,6,7 series seem to have their mainwheels quite far forward - did they need a tail prop when on the ground to stop them overbalancing?
Was wondering why the wings were not further back on the aircraft.
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Jetlagged
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RE: DC4 DC6 DC7 - Balance On Ground

Sun Jul 09, 2006 10:02 pm

Probably not, the main wheels are aft of the centre of gravity. Cargo operators might use tail jacks during loading for safety reasons, as the c.g. can move outside limits.

How about these as well:


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Photo © Nik Deblauwe
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Photo © Frank C. Duarte Jr.


[Edited 2006-07-09 15:05:48]

[Edited 2006-07-09 15:06:33]
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vikkyvik
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RE: DC4 DC6 DC7 - Balance On Ground

Sun Jul 09, 2006 10:51 pm

I don't know specific numbers, but I'd assume that having the engines forward of the wheels (as they are) goes a long way towards the CG being in front of the wheels. Engines are typically pretty darn heavy.

~Vik
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ImperialEagle
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RE: DC4 DC6 DC7 - Balance On Ground

Sun Jul 09, 2006 10:58 pm

Well, after dusting off and looking over my DC-6/7 operating manuals, I have not seen any particular instructions involving the support of the tail for aircraft loading proceedures. So the CG envelope was apparently good for all but the most extreme loading proceedures. Certainly tri-pods would have been used with engines removed as a saftey measure.

I do however remember NW using tri-pod supports under the tails of their DC-7CF's when loading. I also recall (during my days at FLL) the old Caicos-Carribean using tri-pods to support the tails of their DC-4's (somewhere I know I have photo's of that). And I remember Airlift and Riddle using tri-pods to support the tails of their old "windmills" here in ATL back in the good 'ole days.
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SlamClick
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RE: DC4 DC6 DC7 - Balance On Ground

Sun Jul 09, 2006 11:40 pm

My memory tells me that it was probably only needed for cargo ops.

I remember an article in the Navy's aviation safety pub, Approach about an engine change on a Navy C-121 (Connie)

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Photo © Jim Newton


... which has a pretty similar configuration to the planes you asked about.

They pulled the number three engine, mount and all, and put it on a truck. Then the crewchief was standing on the ramp looking up at that big bare firewall and it occurred to him: "Hey! We took a lot of weight off from forward of the CG!" So he decided to put on the tailstand. So he walked up the stairs, boarded the plane, and walked back to the aft end of the cabin to get the stand . . .

Major damage to all three fins and rudders.
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MD11Engineer
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RE: DC4 DC6 DC7 - Balance On Ground

Mon Jul 10, 2006 1:34 am

Quoting NZ8800 (Thread starter):
The DC4,6,7 series seem to have their mainwheels quite far forward - did they need a tail prop when on the ground to stop them overbalancing?
Was wondering why the wings were not further back on the aircraft.

Definitely yes. Years ago I was working on a C-54 (military version of the DC-4) on a museum project. There I also met the guys operating the DC-4 from SAA. The first thing that happened after the plane arrived at it's parking place was the F/E dropping a small bag from the hatch on the r/h side, just aft of the cockpit. It contained the gear down lock "blocks" and the key for the lower deck cargo holds. Then somebody of the ground crew would insert the gear down lock "blocks" and would get the tail stand from the forward cargo hold and install it on the tail skid. Only after this was completed were the passengers allowed to get up and walk to the cabin door, which was aft on the L/H side.
Just prior to departure the tailstand and the locks would be removed, the key and the locks stuck into the bag and the bag hauled up by the F/E by a lanyard.

The position of the wings was most likely determined to provide balance in the air, less so on ground.

Jan

[Edited 2006-07-09 18:36:26]
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2H4
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RE: DC4 DC6 DC7 - Balance On Ground

Mon Jul 10, 2006 1:39 am



The Il-38 always made me wonder about the same thing:






2H4


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GQfluffy
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RE: DC4 DC6 DC7 - Balance On Ground

Mon Jul 10, 2006 3:51 am

Quoting Jetlagged (Reply 1):

Fairchild Metros (and Merlins) are VERY nose-heavy...
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411A
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RE: DC4 DC6 DC7 - Balance On Ground

Mon Jul 10, 2006 4:13 am

Having flown (as a pilot) the DC-6 and DC-7 series aircraft, the tailstand was only required for cargo loading or an engine change, the tailstand was not required for normal passenger operation.
In addition, my father was engineering project manager at Douglas in Santa Monica on both these aircraft, and I still have his engineering notes related to these very fine aircraft.

It also might surprise many to realise that the DC-6B was the most cost-efficient four engine piston transport to operate, on a seat/mile basis....thanks mainly to the Pratt & Whitney R2800 CB series engines fitted.

And, like many Douglas aircraft, were a delight to fly.
 
vc10
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RE: DC4 DC6 DC7 - Balance On Ground

Mon Jul 10, 2006 6:36 am

If I remember correctly all these piston powered airliners tended to load /unload their passengers from the rear door, which is no problem , however when these aircraft such as the DC-4 were converted to freighter the freight door was normally at the rear, which meant that when you loaded a heavy load[which you would want towards the front] on first, the A/C
C of G would go very rearwards and could hazard the aircraft until that heavy load got positioned forward. Now Aircraft like the Connie 1049 could have freight doors fore and aft of the wings so that problem was over come.
On a 749 Connie when off loading a heavy piece of cargo[ which was the last item] through the rear door we actually tied two fifty gal drums filled with concrete to the nose leg to stop the aircraft from tipping on it's tail

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RE: DC4 DC6 DC7 - Balance On Ground

Mon Jul 10, 2006 9:38 pm

In 1972 the USAF "gave" their C-54 ( 47?-545) based in Taipei to the Chinese Air Force when it ran out of airframe time.
The first thing the CAF did after towing it to their hanger was sit it on its tail as a result of all the "new owners" trying to get in for a look at the same time.
We wouldn't tow the plane without a tail stand. A quick start sometimes resulted in the nose coming off the ground.
The Navy with their C-118 thought we were pretty funny with all our safety gear.
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Dougloid
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RE: DC4 DC6 DC7 - Balance On Ground

Mon Jul 10, 2006 10:35 pm

Quoting Jetlagged (Reply 1):
How about these as well:

the one on the right is an oldie. There weren't too many round window Metros made-maybe 4.
If you believe in coincidence, you haven't looked close enough-Joe Leaphorn
 
andz
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RE: DC4 DC6 DC7 - Balance On Ground

Tue Jul 11, 2006 2:00 am

My wife is a flight attendant on the SAA Historic Flight DC-4s and she says that they make an announcement after landing for the passengers to stay in their seats until the tail pole is in place.
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DH106
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RE: DC4 DC6 DC7 - Balance On Ground

Tue Jul 11, 2006 2:05 am

Sounds like the DC-4 is quite critical, but the DC-6 & 7 less so. They're probably more tolerant due to their increased length either side of the CG
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Ratzz
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RE: DC4 DC6 DC7 - Balance On Ground

Tue Jul 11, 2006 3:52 am

-The DC6 is really tricky to load,Atlantic Cargo from Great Britain still use the aircraft together with the L-188 Electra.

-Always a thrill (in a positive way) to work on either one of them,regardless of ground balance problems,hence they don´t make aircrafts like´em anymore  
-Whenever we load/unload the palletised cargo,we always take care in doing it the right way with caution to prevent a tailstrike since they don´t carry a tailstand.

-The last time I worked on the DC6,I ended up doing a visual startup in the middle of the night and removed my headset just to hear the P&W´s roar to life...the crew noticed that I took off my headset and offered me a real treat :
-The first engine they started,they overused the booster pumps thus making the engine fire almost one cylinder at the time,throwing large flames out of the exhaust....I still get goosebumps when thinking about it..  

-Finally,I come to think of a good ol´sayin´:
-"it´s always better with four slow screws than two or more fast blowjobs"..

[Edited 2006-07-10 20:55:13]
 
L-188
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RE: DC4 DC6 DC7 - Balance On Ground

Tue Jul 11, 2006 10:50 am

I have actually put DC-6's hard down on their tailstand while loading two.

This first time we where taking a 15,000 lb generator out of aft cargo door and had to set it down to get a better bite on it wth the forklift.

The other time was putting a bobcat tractor on a swingtail conversion. In that case we picked the bobcat up on the forks of our forklift, the crew had me bring the forklift forward and then push down on the deck of the airplane until it was sitting on the ground...they then drove the bobcat off the forks. The reason they did this was so the tail wouldn't suddenly drop when the bobcat's weight got on the airplane. Could have ended up putting the bobcat through the roof of the cabin if that happened.
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