T 1066/10 10-04-2014

Reasons for the Decision

1. The appeal is admissible.

2. Main request - inventive step

2.1 It was not disputed by the appellant that each of documents D1 and D2, taken separately, discloses a non-aircraft-propelling auxiliary gas turbine engine according to the preamble of claim 1 and that the subject-matter of claim 1 differs therefrom by the features defined in the characterizing portion and referred to as features (a) and (b) in the decision under appeal, namely:

(a) the inlet is adapted to receive bleed air from the aircraft-propelling gas turbine engine, and

(b) the outlet duct of the compressor includes a variable-area bleed valve adapted to bleed air from the outlet duct to the atmosphere.

2.2 As regards distinguishing feature (a), the examining division stated that its effect is not discussed in the application and that it appears to consist in improving the high-altitude performance of the non-aircraft-propelling auxiliary gas turbine engine (APU) above and beyond what can be achieved by using cabin air. The appellant essentially submitted that the distinguishing feature (a) rather solved the problem of providing for a back-up in the event of a failure of one of the sources of pressurized air, i.e. cabin air or air bled from the main engine compressor, to ensure constant auxiliary power supply. The appellant referred to Figure 1's use of a dashed line to represent the receiving of bleed air (23) from the aircraft-propelling gas turbine engine (14) to the inlet (20) of the compressor (18) of the auxiliary gas turbine engine (10) as clearly implying that the supply of bleed air is not intended as the primary supply of air to the auxiliary gas turbine engine. However, even if it is accepted that the supply of bleed air is not intended as the primary supply of air to the auxiliary gas turbine engine, there is no basis in the application as filed to infer that the supply of bleed air provides an alternative or back-up supply of compressed air. Indeed, for achieving this effect, the two sources of air (cabin air or air bled from the main engine compressor) would need to be alternate sources, each of them taken alone being sufficient for providing the required "constant auxiliary power supply", and the engine being able to switch from the one to the other in case of failure. This construction is neither disclosed in the application as filed, nor is it reflected in the wording of claim 1. In fact, the application as filed is silent about how the two sources of air are exploited (separately, together, or according to a specific control strategy). Accordingly, there is no basis to consider a technical effect of feature (a) other than that of improving the performance of the APU, as stated by the Examining Division in point 5 of the decision under appeal.

2.3 It might well be, as argued by the appellant, that the alleged invention as defined in claim 1 does not represent a technical regression. However, when reading D2, which the examining division correctly identified as the closest prior art (it is noted that a reasoning analogous to the one that follows could also be made starting from D1, which also represents an appropriate starting point for the assessment of inventive step), the skilled person is taught that the known arrangements in which the air required for operating the auxiliary gas turbine engine is tapped from the compressor of the main propulsion unit has the disadvantage that the main propulsion unit must be operated, especially at high altitudes, at a higher performance level than flying conditions actually call for (see page 1, second paragraph). D2 further teaches that also the known arrangements in which air is drawn exclusively from the atmosphere have disadvantages, in that they necessitate operating the auxiliary gas turbine engine with increasing flight altitude at an increased performance level (see the paragraph bridging pages 1 and 2). The aim of D2 is that of increasing the power output of the auxiliary gas turbine engine compared with that of an auxiliary gas turbine engine arranged to suck air from the atmosphere (see page 2, second and third paragraphs). To achieve this aim D2 proposes to suck air from the aircraft's cabin. The skilled person, faced with the problem of further improving the performance of the auxiliary gas turbine engine according to D2, would obviously consider that the known measure of tapping air from the compressor of the main propulsion unit would provide a solution to this problem. In fact, as noted above, D2 already refers to this measure and moreover D3 specifically refers to the improved performance resulting from this measure (see in particular paragraph [0024]). Accordingly, the skilled person would consider providing, in addition to the measure of sucking air from the aircraft's cabin, the further measure of tapping air from the compressor of the main propulsion unit (i.e. the above-mentioned feature (a)) in order to solve the above-mentioned problem of improving the performance of the auxiliary gas turbine engine. In doing this, as pointed out by the examining division (see page 4 of the impugned decision, penultimate paragraph), the skilled person would accept the disadvantages of the further measure. In any event, the skilled person would obviously recognize that such disadvantages would be mitigated by the fact that air is not drawn exclusively from the compressor of the main propulsion unit (as in the prior art referred to on page 1 of D2, or in the prior art according to D3) but is also drawn from the cabin.

2.4 The appellant's referred to D4 and submitted that this document teaches that a power pack should be provided to maintain power in the event of system failure. However, since the objective technical problem cannot be seen in how to maintain power in the event of system failure, for the reasons explained above,.this argument is moot.

2.5 As regards distinguishing feature (b) (see points 4 and 6 of the decision under appeal), it is accepted that, although D5 and D6 each disclose bleed valves for bleeding air from a compressor, neither document discloses the use of such bleed valves in an auxiliary power supply gas turbine of an aircraft. However, an auxiliary power supply gas turbine of an aircraft is still a gas turbine operating in a known fashion, which would therefore be subject to surging as the turbines according to D5 and D6. This point, which was specifically mentioned in the communication of the Board referred to in point VII above, was not disputed by the appellant. Accordingly, it would be obvious to provide, in the gas turbine according to D2 (or as modified in the manner explained above by also providing bleed air from the aircraft propelling gas turbine engine), a variable-area bleed valve adapted to bleed air from the outlet duct of the compressor to the atmosphere to avoid surging in accordance with the teachings of either D5 or D6.

2.6 Accordingly, the arguments of the appellant not being convincing, the findings of the Examining Division as to lack of inventive step must be confirmed.

3. Auxiliary request

3.1 At the oral proceedings the Board has decided not to exercise its discretion under Article 12(4) RPBA to not take into account the auxiliary request.

This request fails for lack of compliance with the requirements of Article 123(2) EPC, for the reasons explained below.

Claim 1 has been amended by introducing additional features taken from the description, where they are disclosed in connection with "one extension of the first expression of the embodiment of figure 1" in which "there is included a system (not shown) for enhancing the use of cabin air provided to the inlet of the compressor of the auxiliary gas turbine engine" (see the last paragraph of page 4 of the application as filed).

Accordingly, the additional features introduced in claim 1 are taken from a particular embodiment (said "extension of the first expression of the embodiment of figure 1"). In this particular embodiment, they are disclosed in combination with the feature that the outlets of the system turbine and the system compressor have substantially the same pressure. Omitting this feature from the combination of features of the particular embodiment introduced in claim 1 results in an unallowable intermediate generalisation. In fact, by omitting this feature, claim 1 leaves open whether the pressure at the outlets of the system turbine and of the system compressor are at substantially the same pressure and thus encompasses the possibility that the outlets are at substantially different pressures. Since, however, both outlets are in fluid communication with the inlet of the auxiliary-gas-turbine-engine compressor, different pressures at the outlets would require additional measures, e.g. for equalizing the pressures at said inlet that are not disclosed in the application as filed. Therefore, it is clear that the disclosure of the application as filed is restricted to the possibility that the outlets of the system turbine and of the system compressor have substantially the same pressure. Accordingly, the amendments made to claim 1 introduce new technical information as compared to the disclosure of the application as filed.

3.2 The appellant submitted that the omitted feature represented omission of a functional statement of the effect of the system turbine and system compressor, rather than omission of a structural feature of the system. This argument cannot be accepted because the desired effect of providing substantially the same pressure at the outlets of the system turbine and of the system compressor cannot be seen solely as a result of the operation of the system turbine and of the system compressor, irrespective of their structure, but is also necessarily linked to structural features thereof. In fact, the indication of the desired result implies that structural requirements, such as inlet diameters, degree of compression, power consumption, etc..., must be met. This means that the indication of the desired result to be achieved with the system necessarily implies the presence of suitable structural features for the system itself.

3.3 The Board notes that the issue of unallowable intermediate generalisation under Article 123(2) EPC was already addressed in the communication (see point VII above), although in the context of the issue of admissibility of the auxiliary request under Article 12(4) RPBA (see point 3.5 of the communication). However the appellant, who was absent at the oral proceedings, could have expected the issue under Article 123(2) EPC to be dealt with by the Board if the issue of admissibility under Article 12(4) RPBA turned out in favour of the appellant. Moreover, the appellant specifically commented on the issue of unallowable intermediate generalisation under Article 123(2) EPC in its reply (see point VIII above). Accordingly, the Board is satisfied that the appellant's right to be heard is met.

4. Request for a referral of a question to the Enlarged Board of Appeal (Article 112(1)(a) EPC)

Since the request of the appellant to refer a question to the Enlarged board of Appeal hinges on the refusal of the Board to admit the auxiliary request into the proceedings pursuant to Article 12(4) RPBA, and since the Board has taken into account the auxiliary request, the question is not material to the present decision. Accordingly, the request must be rejected.