AIRCRAFT INVESTIGATION
weight and performance calculations for the Albatros J.I
Albatros J.I
role : armoured ground attack aircraft
importance : ***
first flight : operational : March 1918
country : Germany
design :
production : 240 aircraft
general information :
Ground attack aircraft derived from the C.XII. popular with the crew due to it’s armour plating, 5mm thick chrome nickel steel plating weighing ca. 490 kg. Motor was not protected by armour plating.
Armament aircraft consisted of two fixed guns "Spandau" mounted beneath the fuselage at an angle of 45 degrees
With only the 200 h.p. Benz Bz IV for a power plant (although the actual power output of this engine was closer to 225 h.p. at the low altitudes these aircraft worked), as compared with the 260 h.p. Mercedes D IV installed in the C XII, and an increase of some 350 kg. (770 lb.) in loaded weight, a drastic reduction in performance could only be expected. The reduction in climb performance did not have such serious repercussions as might be imagined, since the operational requirements for this class of machine rarely called for much altitude. When in action they could most effectively fulfil their chief offensive role, harassing the troops in the trenches, at altitudes between 50 and 500 m. (164 and 1,640 ft.).
Unlike the A.E.G. J I, the whole of the nose was not armoured, only the actual cockpit area being covered with 5 mm. chrome nickel steel armour on the sides and underneath. To simplify manufacture the armour on the sides was largely in its original slab sheet form, cut to size, and bolted to the basic structure. To provide maximum protection for the pilot the side armour was not cut away on the front cockpit sides, but to facilitate entry and egress a panel was hinged to fold outwards and down.
The nose sloped down quite sharply from the front cockpit, thereby affording a reasonably good degree of forward vision.
Although use was also made of the complete C XII wing assembly, it was mounted farther forward, with a 2° sweep on each panel to compensate for the added 490 kg. (1,078 lb.) weight of the armour and to preserve the C/G position. Installation of the radiator differed from that of the C XII, a large rectangular cooler being mounted on the centre-section leading-edge.
Due to the altered fuselage contours, it was not possible to use the original C XII undercarriage chassis, although only a slight modification to the steel-tube vee-strut lengths was necessary to employ the majority of the undercarriage components.
Operating in flights of three to six aircraft from the autumn of 1917 onwards, this class of machine was a continual thorn in the side of the Allied ground troops and artillery batteries as their downward-firing machineguns viciously probed and stabbed into trenches, gun pits and horse lines.
users : Luftwaffe
crew : 2
armament : 2 fixed, downwards-firing 7.92 [mm] (0.312 in) Spandau LMG 08/15
machine-guns and 1 movable 7.92 [mm] (0.312 in) Parabellum MG 14 machine-gun for
the observer
engine : 1 Benz Bz.IV liquid-cooled 6 -cylinder inline engine 220 [hp](161.8 KW)
dimensions :
wingspan : 14.14 [m], length : 8.8 [m], height : 3.37[m]
wing area : 43.0 [m^2]
weights :
max.take-off weight : 1808 [kg]
empty weight operational : 1398 [kg] bombload : 0 [kg]
performance :
maximum speed : 140 [km/hr] at sea-level
climbing speed : 120 [m/min]
service ceiling : 4000 [m]
endurance : 2.35 [hours]
estimated action radius : 148 [km]
description :
2-bay biplane with fixed landing gear and tail strut
two spar upper and lower wing
engines, landing gear, fuel and bombs in or attached to the fuselage
airscrew :
fixed pitch 2 -bladed tractor airscrew with max. efficiency :0.64 [ ]
estimated diameter airscrew 3.07 [m]
angle of attack prop : 12.98 [ ]
fine pitch
reduction : 1.00 [ ]
airscrew revs : 1400 [r.p.m.]
pitch at Max speed 1.67 [m]
blade-tip speed at Vmax and max revs. : 228 [m/s]
calculation : *1* (dimensions)
mean wing chord : 1.52 [m]
calculated wing chord (rounded tips): 1.66 [m]
wing aspect ratio : 9.30 []
estimated gap : 1.75 [m]
gap/chord : 1.15 [ ]
seize (span*length*height) : 419 [m^3]
calculation : *2* (fuel consumption)
oil consumption : 2.1 [kg/hr]
fuel consumption(cruise speed) : 47.2 [kg/hr] (64.3 [litre/hr]) at 87 [%] power
distance flown for 1 kg fuel : 2.67 [km/kg]
estimated total fuel capacity : 172 [litre] (126 [kg])
calculation : *3* (weight)
weight engine(s) dry : 370.0 [kg] = 2.29 [kg/KW]
weight 11 litre oil tank : 0.9 [kg]
oil tank filled with 1.2 litre oil : 1.1 [kg]
oil in engine 9 litre oil : 8.1 [kg]
fuel in engine 1 litre fuel : 0.8 [kg]
weight 27 litre gravity patrol tank(s) : 4.1 [kg]
weight radiator : 24.3 [kg]
weight exhaust pipes & fuel lines 14.2 [kg]
weight self-starter : 4.0 [kg]
weight cowling 6.5 [kg]
weight airscrew(s) (wood) incl. boss & bolts : 24.3 [kg]
total weight propulsion system : 457 [kg](25.3 [%])
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weight 5.5 [mm] armour plating engine, crew and fuel tank (9.8 [m^2]) : 420 [kg]
percentage fuselage armoured : 53.5 [%]
armour plating bolted to side of wooden airframe
fuselage skeleton (wood gauge : 6.18 [cm]): 86 [kg]
bracing : 4.5 [kg]
fuselage covering ( 14.6 [m2] doped linen fabric) : 4.7 [kg]
weight controls + indicators: 6.7 [kg]
weight seats : 6.0 [kg]
weight other details, lighting set, etc. : 5.1 [kg]
weight 144 [litre] main fuel tank empty : 11.5 [kg]
weight engine mounts & firewalls : 3 [kg]
total weight fuselage : 547 [kg](30.3 [%])
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weight wing covering (doped linen fabric) : 28 [kg]
total weight ribs (97 ribs) : 107 [kg]
load on front upper spar (clmax) per running metre : 448.2 [N]
load on rear upper spar (vmax) per running metre : 365.8 [N]
total weight 8 spars : 51 [kg]
weight wings : 186 [kg]
weight wing/square meter : 4.33 [kg]
weight 8 interplane struts & cabane : 21.2 [kg]
weight cables (80 [m]) : 6.5 [kg] (= 81 [gram] per metre)
diameter cable : 3.6 [mm]
weight fin & rudder (2.3 [m2]) : 10.4 [kg]
weight stabilizer & elevator (4.8 [m2]): 21.3 [kg]
total weight wing surfaces & bracing : 246 [kg] (13.6 [%])
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weight machine-gun(s) : 43.5 [kg]
weight Schneider ring mounting mg :5.5 [kg]
weight ammunition magazine(s) :7.0 [kg]
weight armament : 56 [kg]
********************************************************************
wheel pressure : 904.0 [kg]
weight 2 wheels (800 [mm] by 101 [mm]) : 31.0 [kg]
weight tailskid : 1.9 [kg]
weight undercarriage with axle 28.0 [kg]
total weight landing gear : 60.9 [kg] (3.4 [%]
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calculated empty weight : 1367 [kg](75.6 [%])
weight oil for 2.8 hours flying : 5.9 [kg]
weight cooling fluids : 35.0 [kg]
weight 1 drums empty : 4.5 [kg]
weight ammunition (3000 rounds) : 89.2 [kg]
weight signal pistol with cartridges : 3.6 [kg]
weight automatic pistol with spare magazines : 1.2 [kg]
*******************************************************************
calculated operational weight empty : 1502 [kg] (83.1 [%])
published operational weight empty : 1398 [kg] (77.3 [%])
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weight crew : 162 [kg]
weight fuel for 2.0 hours flying : 94 [kg]
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operational weight : 1758 [kg](97.3 [%])
bombload could not be carried with fuel for 2 hours flying time
fuel reserve : 31 [kg] enough for 0.67 [hours] flying
possible additional useful load : 18 [kg]
operational weight fully loaded : 1808 [kg] with fuel tank filled for 100 [%]
published maximum take-off weight : 1808 [kg] (100.0 [%])
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calculation : * 4 * (engine power)
power loading (operational without bombload) : 10.87 [kg/kW]
total power : 161.8 [kW] at 1400 [r.p.m]
calculation : *5* (loads)
manoeuvre load : 1.5 [g] at 1000 [m]
limit load : 2.75 [g] ultimate load : 4.1 [g] load factor : 0.9 [g]
design flight time : 1.88 [hours]
design cycles : 138 sorties, design hours : 260 [hours]
operational wing loading : 401 [N/m^2]
wing stress (3 g) during operation : 278 [N/kg] at 3g emergency manoeuvre
calculation : *6* (angles of attack)
angle of attack zero lift : -1.13 ["]
max. angle of attack (stalling angle) : 11.69 ["]
angle of attack at max. speed : 3.81 ["]
calculation : *7* (lift & drag ratios
lift coefficient at angle of attack 0° :0.10 [ ]
lift coefficient at max. angle of attack : 1.14 [ ]
lift coefficient at max. speed : 0.44 [ ]
induced drag coefficient at max. speed : 0.0116 [ ]
drag coefficient at max. speed : 0.0664 [ ]
drag coefficient (zero lift) : 0.0548 [ ]
calculation : *8* (speeds
stalling speed at sea-level (OW): 86 [km/u]
landing speed at sea-level (OW without bombload): 104 [km/hr]
min. drag speed (max endurance) = minimum speed*1.1 at cruise height : 96 [km/hr] at 300 [m] (power:56 [%])
min. power speed (max range) : 111 [km/hr] at 300 [m] (power:64 [%])
max. rate of climb speed : 91.6 [km/hr] at sea-level
cruising speed : 126 [km/hr] op 300 [m] (power:78 [%])
design speed prop : 133 [km/hr]
maximum speed : 140 [km/hr] op 100 [m] (power:99 [%])
climbing speed at sea-level (without bombload) : 149 [m/min]
calculation : *9* (regarding various performances)
take-off distance at sea-level : 193 [m]
lift/drag ratio : 8.66 [ ]
max. practical ceiling : 3850 [m] with flying weight :1513 [kg]
practical ceiling (operational weight): 2875 [m] with flying weight :1758 [kg]
practical ceiling fully loaded (mtow- 1 hour fuel) : 2875 [m] with flying weight :1761 [kg]
published ceiling (4000 [m]
climb to 1500m (without bombload) : 12.01 [min]
max. dive speed : 356.8 [km/hr] at 1875 [m] height
load factor at max. angle turn 1.53 ["g"]
turn radius at 500m: 82 [m]
time needed for 360* turn 16.9 [seconds] at 500m
calculation *10* (action radius & endurance)
operational endurance : 2.63 [hours] with 2 crew and 20 [kg] useful load and 98.5 [%] fuel
published endurance : 2.35 [hours] with 2 crew and possible useful (bomb) load : 33 [kg] and 88.1 [%] fuel
action radius : 165 [km] with 2 crew and 20[kg] photo camera/radio transmitter or bombload
max range theoretically with additional fuel tanks for total 435 [litre] fuel : 852 [km]
useful load with action-radius 250km : 132 [kg]
production : 16.59 [tonkm/hour]
oil and fuel consumption per tonkm : 2.97 [kg]
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Literature :
Praktisch handboek vliegtuigen deel 1 page 293
Wikipedia
DISCLAIMER Above calculations are based on published data, they must be
regarded as indication not as facts.
Calculated performance and weight may not correspond with actual weights
and performances and are assumptions for which no responsibility can be taken.
Calculations are as accurate as possible, they can be fine-tuned when more data
is available, you are welcome to give suggestions and additional information
so we can improve our program. For copyright on drawings/photographs/
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(c) B van der Zalm 23 November 2019 contact : info.aircraftinvestigation@gmail.com python 3.7.4