What airliner type, please?
Join Date: Dec 2014
Location: 40nm east of BLL
Posts: 151
Likes: 0
Received 0 Likes
on
0 Posts
"Underfed Connie": There is certainly not used many rulers at the designshop of De Havilland. it's extreme slick and as it shares the Plywood-construction with the Mossie i wonder if the strenght of the plywood lies in this un-edgy design :-/
Prop' size: Until now I've considered the treshold between two and three propellarblades to be about 700hp, but as it seems that the Fokker are on the limit it might be in the area of this 500hp instead :-/
Maybee the simplicity of the wooden fixed pitch double prop' did delay the decision of upgrading to three blades :-/
Prop' size: Until now I've considered the treshold between two and three propellarblades to be about 700hp, but as it seems that the Fokker are on the limit it might be in the area of this 500hp instead :-/
Maybee the simplicity of the wooden fixed pitch double prop' did delay the decision of upgrading to three blades :-/
Maybee the simplicity of the wooden fixed pitch double prop' did delay the decision of upgrading to three blades
Flybiker's picture is the first one I have seen of an Albatross from that aspect. I am surprised by the very tall undercarriage and the consequent high deck-angle.
It doesn't seem to be needed for prop clearance. Anyone know why it was so tall?
It doesn't seem to be needed for prop clearance. Anyone know why it was so tall?
Most likely the need to keep the take off speeds low. With a lower deck angle and consequently lower AoA on the wing, you need more speed for the same weight to get off the ground.
Join Date: Dec 2014
Location: 40nm east of BLL
Posts: 151
Likes: 0
Received 0 Likes
on
0 Posts
As being of taildragger gear the AoA can't be rised higher than when sitting on the ground, hence the height, wich have to be rised together with the lenght of the fuselage to kee the same AoA.
However, judged on the ladders there might be a little more than two meters between ground and leading edge and I think a grown man can stand upright under the wing of a DC-3, hence the difference might be less than what it seems :-/
However, judged on the ladders there might be a little more than two meters between ground and leading edge and I think a grown man can stand upright under the wing of a DC-3, hence the difference might be less than what it seems :-/
Join Date: Aug 2006
Location: Timbukthree
Posts: 13
Likes: 0
Received 0 Likes
on
0 Posts
Indeed. The tall cockpit height did not go unnoticed by photo-journalists. The AOA of the small aeroplane and the Albatross are actually quite similar.. Plenty of airscrew clearance on both..
Just for the record... The "small aeroplane" is the TK4 G-AETK.
DH.91 Albatross
In 1940, A.C. Kermode was evidently struck with the streamlined efficiency of the Albatross design, as was D.P. Davies with that of the Boeing 707 two decades later. Interesting that its total power was not much different from the DC-3**.
What a super photo (as always), evansb. Interesting cowlings for the inverted V12, air-cooled Gypsy 12s.
Ahhh, de Havilland... Perhaps we need an Albatross thread.
** [EDIT] There seems to be some confusion on the sea-level T/O power of the DH Gypsy 12: was it 425 HP or 525 HP? Another comparison with the 1100 HP Wright Cyclones or the 1200 HP Twin Wasps of the DC-3 might relate to the effectiveness of their respective superchargers at cruise altitude. I now see that, as well as having a longer fuselage and wingspan, the MTOW of the Albatross was higher than that of a DC-3 or civil-registered C-47. It was a lot faster, but the quoted range (always a bit nebulous unless a payload is quoted) seems a bit limited for trans-Atlantic ops.
What a super photo (as always), evansb. Interesting cowlings for the inverted V12, air-cooled Gypsy 12s.
Ahhh, de Havilland... Perhaps we need an Albatross thread.
** [EDIT] There seems to be some confusion on the sea-level T/O power of the DH Gypsy 12: was it 425 HP or 525 HP? Another comparison with the 1100 HP Wright Cyclones or the 1200 HP Twin Wasps of the DC-3 might relate to the effectiveness of their respective superchargers at cruise altitude. I now see that, as well as having a longer fuselage and wingspan, the MTOW of the Albatross was higher than that of a DC-3 or civil-registered C-47. It was a lot faster, but the quoted range (always a bit nebulous unless a payload is quoted) seems a bit limited for trans-Atlantic ops.
Last edited by Chris Scott; 6th Jan 2016 at 15:32. Reason: ** added. Typos. 2nd para added.
Which helpfully dates the photo to the latter half of 1937. The race number on the tail was presumably for that year's King's Cup Air Race, held at Hatfield on 11th September, where no doubt the photo was taken, and three weeks before the TK4 was destroyed in a fatal crash.
Yes, and for the benefit of those that don't know I'll point out that the cooling air for those air-cooled motors entered through those round intakes on the wing LE, thence flowing forward past the cylinders.
Not sure how this contributes as although the power per motor was much the same, I believe the Beech King Air had two motors and as can be seen the Albatross had four.
Not sure how this contributes as although the power per motor was much the same, I believe the Beech King Air had two motors and as can be seen the Albatross had four.
Courtesy of Flight, June 23rd, 1938:
Maximum power rating: 410/425 bhp at 2400 rpm at 7500 ft, zero boost
Maximum take-off power: 505/525 bhp at 2600 rpm at sea level, 3½ psi boost
I assume ZeBedie is referring to the King Air 300/350, powered by the 1050 shp PT6A-60A, resulting in a twin with the same installed power as the DH91's four Gipsy Twelves.
Join Date: Dec 2007
Location: Cyprus
Age: 91
Posts: 179
Likes: 0
Received 0 Likes
on
0 Posts
May I suggest that the length of the Albatross main undercarriage leg was governed by the distance from it's hinge near the inboard nacelle to the nearest stowage place for the wheel, in the fuselage? Angle of attack had nothing to do with it, tail-draggers didn't take off with the tail-wheel still on the ground.
Albatross - DH Gipsy 12 power figures
Quote:
"Courtesy of Flight, June 23rd, 1938:
Maximum power rating: 410/425 bhp at 2400 rpm at 7500 ft, zero boost
Maximum take-off power: 505/525 bhp at 2600 rpm at sea level, 3½ psi boost"
Thanks, Dave, the confusion resulted from my narrow research, limited to the separate Wiki entries for the Albatross and the Gypsy 12. The former gives 525 hp, but the latter states:
"425 hp at 2,450 rpm at 0 psi boost (five minutes maximum)"
Assuming the latter is authentic, perhaps it was a limitation used for T/O at an early stage in development. One can understand the reduced boost, but interesting that the rpm is also limited. I wonder if the crew controlled rpm with a separate "pitch" lever, as is the norm on piston engines with constant-speed props (including the contemporary Twin Wasp). The Gipsy Queen on the post-war, 4-engined Heron had a combined throttle/rpm lever (whereas on the Dove, with its supercharged engines, they were separate, IIRC). If the Gipsy 12 was the same, it might explain the 2450 rpm limit quoted above. If, on the other hand, the pitch (rpm) lever was separate, setting up all four engines at 2450 rpm for T/O would have required careful handling, particularly on bumpy grass airfields.
Quote from Allan Lupton:
"Yes, and for the benefit of those that don't know I'll point out that the cooling air for those air-cooled motors entered through those round intakes on the wing LE, thence flowing forward past the cylinders."
And presumably also to the carburetors? I wonder if the cylinder-head temp control was automatic in the cruise.
"Courtesy of Flight, June 23rd, 1938:
Maximum power rating: 410/425 bhp at 2400 rpm at 7500 ft, zero boost
Maximum take-off power: 505/525 bhp at 2600 rpm at sea level, 3½ psi boost"
Thanks, Dave, the confusion resulted from my narrow research, limited to the separate Wiki entries for the Albatross and the Gypsy 12. The former gives 525 hp, but the latter states:
"425 hp at 2,450 rpm at 0 psi boost (five minutes maximum)"
Assuming the latter is authentic, perhaps it was a limitation used for T/O at an early stage in development. One can understand the reduced boost, but interesting that the rpm is also limited. I wonder if the crew controlled rpm with a separate "pitch" lever, as is the norm on piston engines with constant-speed props (including the contemporary Twin Wasp). The Gipsy Queen on the post-war, 4-engined Heron had a combined throttle/rpm lever (whereas on the Dove, with its supercharged engines, they were separate, IIRC). If the Gipsy 12 was the same, it might explain the 2450 rpm limit quoted above. If, on the other hand, the pitch (rpm) lever was separate, setting up all four engines at 2450 rpm for T/O would have required careful handling, particularly on bumpy grass airfields.
Quote from Allan Lupton:
"Yes, and for the benefit of those that don't know I'll point out that the cooling air for those air-cooled motors entered through those round intakes on the wing LE, thence flowing forward past the cylinders."
And presumably also to the carburetors? I wonder if the cylinder-head temp control was automatic in the cruise.
Last edited by Chris Scott; 7th Jan 2016 at 10:51. Reason: Clarification on Gipsy Queen controls.
If that was the case, why didn't DH just position the pivot further inboard, resulting in a shorter leg?
Join Date: Jun 2014
Location: eastcoastoz
Age: 76
Posts: 1,699
Likes: 0
Received 0 Likes
on
0 Posts
The tall U/C question was raised on a thread a while ago relating to the Short Stirling.
ISTR that aircraft's need for a gangly and complicated undercart was explained by the need to maintain a certain ground-sitting angle.
Because its fuselage was much longer (compared with the Lancaster and Halifax), the extra mains height was needed to achieve said angle.
I went away scratching my head and still none the wiser as to why an aircraft would NEED to ground-sit at that angle.
Prop-tip clearance and bomb-loading requirements would not have been a factor in that case, I'm sure.
In the case of the Albatross, the wing thickness where it abutted the fuselage was, from memory, something like 28 inches.
I would have thought that was adequate depth for the wheel and associated 'struttery
So... I'm still stumbling around hoping someone can explain that mystery for me.
ISTR that aircraft's need for a gangly and complicated undercart was explained by the need to maintain a certain ground-sitting angle.
Because its fuselage was much longer (compared with the Lancaster and Halifax), the extra mains height was needed to achieve said angle.
I went away scratching my head and still none the wiser as to why an aircraft would NEED to ground-sit at that angle.
Prop-tip clearance and bomb-loading requirements would not have been a factor in that case, I'm sure.
In the case of the Albatross, the wing thickness where it abutted the fuselage was, from memory, something like 28 inches.
I would have thought that was adequate depth for the wheel and associated 'struttery
So... I'm still stumbling around hoping someone can explain that mystery for me.
Re the height of the nose with tail-wheel down, the deck angle does look to be a bit steeper than the DC-3, and the fuselage length is over 10% greater. To obtain enough AoA to become airborne on short fields (flapless) **, the respective riggers' angles of incidence would also come into the equation.
In Flybiker's photo, the apparent nose height may be exaggerated, because the men are standing further from the camera than is the nose.
On a different matter, the YouTube video shows a very different tail-fin assembly from all the photos posted above.
** [EDIT] ...and to avoid striking the tail-wheel first on a short-field (slow) landing...
In Flybiker's photo, the apparent nose height may be exaggerated, because the men are standing further from the camera than is the nose.
On a different matter, the YouTube video shows a very different tail-fin assembly from all the photos posted above.
** [EDIT] ...and to avoid striking the tail-wheel first on a short-field (slow) landing...
Last edited by Chris Scott; 7th Jan 2016 at 14:15. Reason: ** added.
Join Date: Jun 2014
Location: eastcoastoz
Age: 76
Posts: 1,699
Likes: 0
Received 0 Likes
on
0 Posts
I haven't seen the video, Chris - but if the fins are in-set on the tailplane, that set-up, on the two prototypes,
was found to give insufficient directional stability.
was found to give insufficient directional stability.