Smithy and P.G. Taylor both claim that Wackett added only two (2) extra wing tanks, whereas Wackett himself later claimed , in a 1974 lecture, that he added four (4). It is believed that this recollection was incorrect. However, all three basically agree on the total capacities of the extra tanks. It should be noted that the two Wackett wing tanks were removed by Lockheed after the Pacific flight although the Wackett fuselage tank under the pilot's seat was retained. (See "How Many Wackett Tanks?" below)

Although most sources state that Wackett added three tanks to the Altair (2 wing, 1 fuselage), Sir Lawrence Wackett himself later claimed to have added five tanks (4 wing, 1 fuselage). The following message, sent in response to a request from the Controller of Civil Aviation, by the District Superintendent of Civil Aviation at Mascot (Sydney) on 10th October 1934, provides another perspective:

" IMPORTANT Your 1453/9. USB full details one additional fuel tank forty gallons capacity being installed each wing. Tanks centre line located 12 feet from centre line aircraft. These tanks mounted in metal straps and felt attached to spar webs similar to D.H. 80. Fuel leads connect with adjacent wing case. One extra tank 24 gallons being installed under front pilot seat final mounting and fuel connection not yet decided. Additional weight of tankage 62 pounds, fuel 760 pounds, this increases tare to 3737 pounds Total fuel 3817 pounds. All up load 7522 pounds."

(Source: National Archives of Australia Series: MP 113/1 Item: VH/USB PT 3)

Considering that this message was sent within a day or so of a first hand observation (of 2 wing tanks), it must be given greater credence than Sir Lawrence Wackett's recollection (of 4 wing tanks) forty years after the event! However, it should be noted that there is an apparent error in DSCA's addition and he has also failed to allow for the weight of crew, equipment, radio and oil as stated on the Australian CofA. Furthermore, it will be noted that the stated capacities of the added tanks are at variance with those derived from other sources. This raises the question of whether or not Wackett and/or Smithy were forthcoming with accurate capacities or if the DSCA estimated the capacities of the three added tanks. Whilst we may never have a definitive answer, it can be seen from the following table that the maximum variance in the total capacity of the three Wackett tanks is only a mere 8 gallons.

The DSCA's Weight Calculations

As there are several anomalies with the weight calculations in the DSCA's message, we need to examine these. As mentioned previously, in addition to an apparent arithmetical error, no provision has been made for crew, equipment, radio and oil.

By adding the weight of crew, equipment, radio and oil (from the CofA) and by reducing the total fuel to 3708 lbs as calculated in Table 2, we arrive at the following:

Again, we may never have a definitive answer, but the preceeding figures suggest that the Altair, in its Pacific flight configuration, may have been significantly heavier than estimated by the DSCA.