2016/17 Contest Year
20 – 23 APRIL 2017

Q & A

Download 2017 DBF Rules

Teams whose Proposals were accepted for the 2017 DBF (deadline 31 October 2016)

Teams who submitted Design Reports for the 2017 DBF (deadline 22 February 2017)

Download Full Q&A

DBF Q&A #1 - 13 December 2016

Q1.  Will pucks be provided at the competition site, or can we bring our own pucks to fly? Specifically, can we glue our pucks together to better secure them for flight, or will we be dealing with individual provided pucks?

Answer:  The teams will be required to bring their own hockey pucks.  The pucks must be presented individually to the tech inspectors for verification of conformance and the pucks must be secured inside the aircraft for flight.  Any additional features to secure the pucks is at the discretion of each team, but all features will be included in the aircraft empty weight.


Q2.  Can the aircraft have a removable lock pin?

Answer:  All features must be self-locking.  A removable locking pin for locking in the flight condition does not meet this requirement.


Q3.  Regarding the folding wing rule.

“All surfaces or aircraft features described above must securely lock in the flight condition without the use of tools or manual release or engagement of any locking features (in other words, all locking features must be self-locking)”

Does this mean that I am not allowed to touch any mechanism that will be responsible for locking the wing in place?

Answer:  That is correct.  It will be allowed to unlock the mechanism, but not for locking.

Q4.  Is the use of a "pusher" propulsion system allowed for this year’s competition? They have been allowed in the past, but due to the hand launching nature, we want to be sure this is still allowed.

AnswerPusher propulsion is allowed.  The Flight Director is responsible for safety among other things on the flight line and it is at his discretion and final decision if a launch attempt can be executed safely for any aircraft configuration.

Q5.  What will the units be measured in for the Rated Aircraft Cost (RAC)? (ie. lbs, ft, m, N)

Answer:  US/English system of measurement:  pounds (lbs), inches (in), seconds (s).  The final competition rules were updated to clarify this as well as the number of significant digits to be recorded for each value.


Q6.  We had a question involving how the wing tip test is applied to a bi-plane. Since we will have 2 wings will the wing tip test be done on one set or can the load be spread between the two? If the load cannot be split, can we decide which wing is used for the test or must both wings each pass the test?

AnswerIf the load can be clearly shown to be carried by a single wing into the main attachment on the fuselage, then a single tip test of that wing is all that is required.  In the event it cannot be demonstrated sufficiently to the tech inspector, a tip test of each wing will be required.  The tech inspector has final say regarding this requirement.  The best approach is to assume that a tip test will be required on each wing. 


Q7.  I have a question about securing the wings whilst stowed in the launch tube. Are we allowed to use a strap to ensure the wings are secure? For example a Velcro strap, that is completely detached from the aircraft.

Answer:  No.  All moveable features or surfaces must be free to move to the flight condition upon exiting the tube.


Q8.  Could you please confirm if the following design concepts are allowed in the competition:

       A) For storage, the UAV is placed inside a 2-piece foam mold casing (two halves of a cylindrical tube with the inside molded to the contours of the folded UAV). The UAV inside foam mold casing is then slid into the tube from one end.

       B) The storage tube is a 2-piece cylinder (two halves of a cylindrical tube) with a hinge to allow the tube to be opened. The storage tube is lined with a foam molded to the contours of the folded UAV. For storage the UAV is placed inside the opened storage tube and then the storage tube is closed with a hinge.

Answer:  8a – Yes as long as the casing is free to fall off of the airplane without manual removal (i.e., gravity only);  8b – No, the airplane must exit from one of the ends of the tube

Q9.  Are we allowed to stick Velcro to the hockey pucks before placing them in our plane?

Answer:  See answer to question #1 above.  Also, the Velcro must be removed from the hockey pucks for measuring the empty weight of the airplane after each successful mission.  It will be up to the teams to do this in a timely manner after a successful mission. 


Q10.  Are we allowed to use off the shelf folding propellers?

Answer:  Yes


Q11.  I wanted to ask if the foldable surfaces on the aircraft can be folded or held in place only by use of springs and magnets, without any fixed hinge.

Answer:  Springs and magnets are not considered sufficient mechanical attachments for securing features on the aircraft. 


Q12.   Is the person launching the aircraft from his/her hand allowed to run during the launch? If yes, are there any restrictions? For example the distance that he/she can run.

Answer:  Running is allowed and there is no distance restriction.  The aircraft must be released prior to crossing the start/finish line.


Q13.    Is there a limit on what can be considered to be part of the tube? Would lining the inner part of the tube with bubble wrap be against the rules?

Answer:  Dunnage such as bubble wrap is allowed and will be included in the empty weight of the tube.


Q14.  If we decide to use a high lift device during takeoff, such as a flap, can we use our transmitter to move the flap into the desired flight condition right before we hand launch our plane? Or, would the flaps need to be in that desired position when it is stowed in the tube?

AnswerAny servo actuated surface or feature that is controlled through the transmitter can be placed in any position in the tube the team desires and can be actuated with the transmitter at any time prior to or during the flight.


Q15.  We wanted to check into the feasibility of a friction fit design component for the DBF 2017 competition. The rules state that all parts must be self-locking. We are currently considering a tail boom that rotates and/or extends into flight-ready position and stays in place using a tightly fitted brace connecting it to the main wing. Does this design meet the requirement of a captive mechanical mechanism?

Answer:  Friction is not an acceptable locking mechanism

DBF Q&A #2 - 31 January 2017

Note of further definition of moving surfaces or features to the flight condition and self-locking mechanisms:  The design intent of this rule is related to the requirement that in tactical applications, when an UAV is ejected from its launch tube, it must transition from the stored condition to the flight condition without any outside assistance.  All power to achieve this is in the form of stored energy – mechanical, electrical, chemical, pyrotechnic, pneumatic, etc.  In the interest of safety and to also allow the design effort to focus on the aircraft, the intent of the rules is to allow the ground crew member to manually move or rotate surfaces or features in place of this stored energy.  This does not allow the ground crew member to determine how far to move or rotate a surface or feature.  This also precludes any surfaces or features to be manually positioned or aligned since this cannot be done in a tactical scenario.  The ground crew operator cannot align the self-locking device, it must be self-aligning and self-engaging.  All movement must be through a captive mechanical mechanism – at no time can any part of the airplane separate from the airplane, even with the pieces being connected by a lanyard, rubber band, bungee cord, string, rope, etc.

Q1. We have question regarding the feasibility of one of our design choices within the confines of the rules, specifically this passage: "All surfaces or aircraft features must "move" to flight position using hinges, pivots, or other captive mechanical mechanisms. Surfaces or aircraft features cannot temporarily separate from the aircraft and use "lanyards" or similar devices to provide a connection to the aircraft with the operator controlling the path the surfaces or aircraft features takes from stowed to flight position". We intend to have struts attaching the outer wings to the fuselage via ball links. These mechanisms allow for pivoting at each end of the strut, and lock the strut into place when both are secured. During the storage configuration, we would detach the strut from the fuselage manually without tools. The strut would still be attached via the ball link to the outer wing, but not attached at the fuselage. Would this constitute a "lanyard" and therefore violate the rule?

Answer:  Nothing can be detached, manually or otherwise, during deployment of any surfaces or features.  “Captive mechanical mechanisms” in the rules clearly asserts this requirement.


Q2. Regarding the movable surface requirements, we came up with two different options for self-locking mechanism.  The first one is a rubber band between wing and fuselage. For locking, a nest that locks the wing at flight condition. The second one is a seatbelt mechanism that locks the wing which is moved manually to that place.  Are they suitable for the restrictions?

Answer:  Rubber bands are not sufficient self-locking mechanisms as they do not provide a positive lock.  A seat belt type mechanism would be acceptable as long as it self-aligned – no manual intervention for alignment will be allowed. 


Q3. All  surfaces  or aircraft features  must  "move"  to  flight  position  using  hinges,  pivots, or  other captive  mechanical  mechanisms.   Surfaces  or aircraft  features  cannot  temporarily  separate  from the aircraft  and  use  "lanyards"  or  similar  devices  to  provide  a  connection  to  the  aircraft with the operator  controlling  the  path the  surfaces  or aircraft features  takes  from  stowed  to  flight  position.  The question is are "lanyards" or similar devices allowed or not for the purpose listed above?

Answer:  Lanyards are not an acceptable “captive mechanical mechanism” as defined in the rules.  See clarification above.


Q4. Does a 2 degree of freedom ball joint count as an appropriate pivot mechanism, or is it similar to the forbidden lanyard in that it will "provide a connection to the aircraft with the operator controlling the path the surfaces or aircraft features takes from stowed to flight position?”

Answer:  Ball joints are acceptable captive mechanical mechanisms. But, the operator can move the features and surfaces but CANNOT align the surfaces to the self-locking position.  It must be self-aligning and self-positioning in addition to self-locking.


Q5. Can the tube separate in places other than the end caps?

Answer:  No.  The airplane must be loaded and removed from one end of the tube.


Q6. What qualifies as "damage" to the UAV after the ground mission?

Answer:  Damage will be determined by the ground mission judge, but is classical in its definition.  Any dents, cracks, scratches, breakage, etc. that is caused by the act of dropping the launch tube with the airplane inside during the ground mission is not allowed.  The launch tube must protect the airplane.

Q7. Q11 on the current Q&A asks if springs and magnets, without a fixed hinge, are allowed; the answer provided was no. Are magnets allowed as an attachment mechanism if there is a fixed hinge?

Answer:  Magnets are not an acceptable locking feature.


Q8. Must all elements "lock" in place, even non-structural elements? For example, would spring-loaded wires on wingtips be allowed? Such a configuration would have these wires fold down for storage but spring into place during flight.

Answer:  The rules do not distinguish between structural or non-structural features or surfaces.  All surfaces or features that move from a position in the stowed configuration to a different position in the flight condition must be self-locking.


Q9. Where is the distinction made between a locking element and an aircraft component, particularly if the two are integrated? For example, a stand-alone clasp surely counts as a locking element and must be self-locking; however, what if a clasp was integrated into the aircraft, such that moving an element of the aircraft into position secured the clasp?

Answer:  Self-locking elements are only required to secure surfaces or features that are moved from the stowed configuration to the flight configuration.  Any other locking features are for other applications are not bound by this requirement.


Q10. May a fairing be used to house a locking element? A fairing would be part of the aircraft structure, and should therefore be able to be moved into flight position?

Answer:  Location of locking mechanisms within the aircraft are at the discretion of the teams.  If a fairing must be moved to engage the locking mechanism, then it becomes a moveable surface or feature and must have its own self-locking mechanism.  A fairing could be fixed and could be part of the surface or feature that is being moved, but if it moves separately, it must have its own self-locking feature.


Q11. Is Velcro allowed as a self-locking mechanism? In this sense, two components could come together with Velcro pre-attached to them (no application of the Velcro, e.g. a strip).

Answer:  No.


Q12. The rules state that components may not be moved via string or lanyard. Is string allowed as a stand-alone structural element? In this sense, the piece of string would be a taut structural element during flight (wing support), but under no load when stored; therefore, when stored, the string would be non-rigid and moveable, but it would still not enable the free movement of any pieces but itself.

Answer:  Strings or lanyards cannot be used in place of captive mechanical mechanisms for moving or rotating surfaces or features into the flight condition.  A string that is permanently attached at both ends that becomes taught in the process of moving or rotating the surface or feature to the flight condition and locking in place is allowed, but no adjustment to the string or its tautness is allowed and the position of the string cannot be controlled by the ground crew (i.e., the string cannot be touched during deployment of the surfaces or features)

Q13. Since the teams will be providing their own pucks ("Q1." of Q&A section), is there a tolerance for the dimensions and weight of each puck? Pucks we have purchased commercially were advertised as "Regulation Hockey Pucks", but according to our scale each puck weighs about 5.2 oz.

Answer:  The regulation weight of the hockey pucks are defined in the rules – 5.5 – 6.0 ozs.  This will be verified during tech inspection.


Q14. The rules and Q&A state the mechanism must be "self-locking" upon exiting the tube and the mechanism does not need to be spring loaded. However, does the aircraft require two locking positions: one inside the tube (stored condition) and one in flight condition? Or is the aircraft able to be taken from the tube and folded and locked into flight condition without "unlocking" it from the stored condition?

Answer:  Locking features in the stored condition inside the tube are not required.  However, if a team choses to implement a locking feature in the stored condition for surviving the ground mission as an example, it cannot be manually released by hand or tools.  It must be “released” by movement of the surface or feature by the ground crew member only.


Q15. We have a question regarding the mounting of the Payload and Batteries:  Is it allowed to use screws to mount the battery to the plane (with fixed Nuts on the battery pack)?  Is it allowed to use screws to secure the pucks (cargo bay cap secured with 4 screws), because in our design the cargo bay cap has to hold the weight of the pucks inflight? Changing of battery and cargo would require ~45 seconds, because one has to take out the screws and tighten them again.

Answer:  How each team choses to secure batteries and payloads is at their discretion.  During tech inspection, the method to secure all internal components and payloads will be inspected to assure it will not come lose during flight.  And no components, internal or otherwise, can come lose as a result of the drops during the ground mission.


Q16. The team has developed a mechanism, where the structural elements are two pins and an elastic band that holds the halves of wings together as shown on picture in the attachment. We would like to know if our design is in accordance with rules.

Answer:  Elastic bands are not acceptable as self-locking mechanisms.  Additionally, pins or other alignment features must be self-aligning as described above.  So positioning or aligning of features by the ground crew member during deployment of surfaces or features to the flight condition is not allowed.

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