Q A_Round_8_(4-3-13).pdf

DARPA-BAA-13-19

VTOL X-Plane

Questions and Answers – Round 8 03 April 2013

VTOL X-Plane BAA-13-19 Questions & Answers – Round 8

IN THE EVENT OF ANY INCONSISTENCY BETWEEN THE ANSWERS PROVIDED

HEREIN AND THE BAA, THE BAA SHALL TAKE PRECEDENCE

Q77. Can the speed of 300 knots to 400 knots be met at 30,000 feet if the speed at sea level is less than 300 knots?

o A77. See Q&A Round 6, question #53.

Q78. If speed varies with altitude and 300 knots is attained at sea level and 400 knots at 30,00 feet, how would DARPA rate the speed of proposal, relative to speed of other candidates?

o A78. The BAA asks that the proposers substantiate their ability to achieve sustained cruise at flight speeds above 300 kt. There is no ranking of proposals. Proposals will not be evaluated against each other since they are not submitted in accordance with a common work statement. Rather, they will be evaluated on the basis of their individual merits. Evaluation of proposals will be accomplished through a scientific/technical review of each proposal. Any and all concepts/configurations that meet the objectives will be considered based on the feasibility of the submitted proposal and available funding. There is no predetermined preferred design configuration of interest to DARPA.

Proposers are asked to exemplify the attributes of their concepts.

Q79. Please define "equivalent actuator disc area." For example, for the V-22, would the equivalent actuator disc area be total disc area of prop-rotors less the planform area of the wings below the total area, less planform area of the engine nacelles?

o A79. The equivalent disk area is the effective disk area of the actuator disk of the lifting device. Traditionally, this disk area is defined as the (circular) area swept by the rotor blades. Wings and nacelles may result in aerodynamic interference, but such effects are accounted for separately, and not by the removal of this area from the disk area. For configurations in which the central hub or spinner region may account for a significantly large portion of the area swept by the blades, the equivalent disk area should be computed based on the effective annulus of the lifting device.

Q80. Please define what would be the "effective disc area of the rotors" for the V-22.

o A80. The equivalent actuator disc area for the V-22 is 2*π*R^2 where R is the radius of the disc.

Q81. Does "equivalent" in "equivalent actuator disc area" intend to take into account viscous, induced and compressibility effects in a rotor such that the equivalent actuator disc area of the rotor is smaller than the geometric disc area of the rotor?

o A81. No.

Q82. Please give an example of equivalent actuator disc area for the case of contrarotating coaxial rotors in close proximity with each other. The total geometric disc area of the two rotors is 2(3.1416 R^2), where R is the radius of each of the two rotors.

o A82. The equivalent actuator disc area for coaxial rotors is 1*π*R^2 where R is the radius of the disc.

Q83. Consider the case of a small company that submits as a Prime Contractor a proposal that DARPA feels merits funding under Phase I, but the small company does not have the resources to qualify for Phase II and Phase III.

(a) Does it mean that even though DARPA feels the proposal should be funded in Phase I on technical merits, it will not fund Phase I because it will not have the resources to qualify for Phase II and III?

(b) If (a) above were the case, could the small company transfer its status as prime contractor during Phase I, or at the end of Phase I, to a larger company that has adequate resources for the work of Phases II and II, and on that basis the small company receives funding under Phase I at least until transfer of Prime Contract status is attained?

(c) Could you please indicate another solution to the problem of (a) above?

o A83. Phase II prime contractors will be limited to Phase I prime contractors who were successful in meeting Phase I performance objectives. The prime contractor must remain the same for all phases of the program; however, subcontractors and subcontractor teaming may be changed. DARPA has not specified a percent work share for prime contractors. If you deem that your organization does not have the integration or fabrication facilities/resources available to perform Phase II, then it may be in your best interest to subcontract that portion of the work out.

Q84. DARPA’s response to Question #22 from Round 5 stated: “It is DARPA’s intent to fund a VTOL solution that meets the objectives specified in the BAA.” Are proposers to deduce from that answer that all offerings must strictly meet or exceed ALL DARPA performance and weight/weight fraction criteria to be compliant? Some concepts may meet or even substantially exceed most metrics such as speed, hover and cruise efficiency, and be marginally shy on others such as useful load fraction. Would such concepts be considered for award?

o A84. It is DARPA’s intent to fund a VTOL solution that meets the objectives specified in the BAA. All proposals will be evaluated against the stated performance objectives, as well as all other evaluation criteria listed in the BAA. Proposals will not be evaluated against each other, but will be evaluated as to their level of value to the Government.

Awards will be made accordingly. Proposers are encouraged to offer the best solution to address the given performance objectives.

Q85. Due to the quick response required for this BAA, offerors will be pushed toward simplified analysis over detailed simulation. In the case of performance analysis of highly cruise-efficient turboshaft-powered aircraft, simple Breguet methods tend to vastly over-estimate achievable performance (sometimes by a factor of 1.5 - 3) because they assume constant L/D, propulsive efficiency, and engine SFC throughout a mission or mission segment. Higher fidelity methods that accurately account for engine RPM limitations and increased SFC at low power levels predict substantially lower endurance and range.

Questions:

a) If our proposal provides performance results using both simplistic Breguet analysis and high-fidelity simulation, will the government utilize both results in evaluating aircraft performance in order to provide a common basis for evaluation?

b) How does the government intend to assess the credibility and accuracy of performance claims; will the government use engine-manufacturers’ performance-estimation programs to spot-check these claims?

o A85. The government evaluation team, including both evaluators and subject matter experts, understand the limitations and constraints of the different methods presented in this question. The evaluation team and support staff members are experts in their fields and have the ability to provide a thorough and substantive review of performance claims.

Proposers are encouraged to provide as much analysis, information and data as possible to substantiate and provide confidence in their performance claims. The Government team will use any means necessary to validate/verify performance claims made, which could include manufacturer’s performance estimating software, operating manuals, etc.

Q86. It is conceivable that an aircraft designed to have the potential for real applications could be of enhanced value over a pure technology demonstrator, and could provide a better means of forecasting performance of a production aircraft. That stated, it appears the weight requirement of the BAA can be satisfied by loading the demonstrator aircraft with dense materials. Is this true?

If so, the internal volume required for the demonstrator presumably would be significantly less than that otherwise necessary for a production aircraft to hold cargo / passengers. A concern is whether the result could be a technology demonstrator offering performance that may not be harnessed / realized in a useful production aircraft. So, while the BAA makes clear the program “is not intended to create a pre-production type aircraft,” will any weight be afforded to proposals for demonstrators having practical production applications?

o A86. DARPA is not looking for an air vehicle built to production standards. DARPA is soliciting an experimental aircraft to demonstrate the performance objectives of the BAA with scalability to heavier and lighter aircraft with operational relevance. The potential military utility of the aircraft is an evaluation criteria and of significant relevance. Thus, fractionated payloads or payloads simulated by the distributed application of dense materials are not a demonstration of practical capability or utility. Please also see the payload discussion on page 29 of the BAA.