Please remember that questions submitted prior to the entry deadline of 31 October that were not answered in the FAQ must be resubmitted.

Be sure to re-check the Rules, FAQ and prior Q&A issues before submitting questions to avoid duplication.

Latest additions are in blue, but you should re-check all items in case you missed any!

DBF Q&A                                                                        12 Feb 2012

Common Topics:

General Questions

Q: Why does the team member name and grade information for my team shown on the teams web page look funny?
A: Information supplied is automatically processed.  If you didn't follow the instructions exactly then your information will not format correctly.  We will accept updates to the team member list in the spring (See the FAQ) and you may try again then.

Q: There was no mention of plane names on the entry form. Will the teams be able to submit plane names this year?
A: Since there is only one team per University team/plane names are not required to differentiate entries, we will use the University name to identify each team.

Q: Are we allowed to present our results in the SI unit system in the technical report ?
A: Teams may use English units, SI units, or both as long as they are consistent and clear to the report judges.

Q: Will spotters be allowed to aid the pilot for Mission 3?
A: Read the rules for information on the flight line crew (observer).

Q: For mission1 how will be the laps counted.  Can we get a score for a partial lap?
A: Read the rules for how laps are timed/counted.  Only complete laps are included in the score.

Q: What are the tolerances for dimensions required by the rules? How will they be measured or verified?
A: We will use commercial rulers or gauge blocks made using/from commercial rulers.  Dimensions will not be at "micrometer" levels.  We will use a commercial scale for all weights.  The contest scale is the official weight.

Q: Do we have a restriction about dimensions of the box we'll use to contain plane and other stuff.  Will the plane be weighed with the box or not?
A: Read the rules, there is no mention of a "box" in this years rules.

Q: Do teams need to "assemble" their aircraft when they enter the assembly area before a flight?
A: Read the rules.  There is no aircraft assembly requirement in this years rules.  Payload loading requirements are listed in the rules.

Q: Does the "5 minute" assembly time limit apply to payload changes during the tech inspection as well?
A: There is no specific time allotment for the tech inspection, or payload changes required during the inspection, however teams should be prepared to go through the tech inspection process efficiently.  If a team is not ready to continue through the inspection sequence the inspectors have the authority to ask the team to return to complete the inspection the next time their number comes up in the inspection queue rotation which can be minutes, hours, or even a day later..

Q: Are battery pack(s) limited to 1.5 lbs/pack or 1.5lbs/plane? The rules say 1.5lbs/pack, but one could conceivable have multiple 1.5 lb packs on the plane and not violate the rules.
A: The weight limit is the weight of all propulsion battery pack(s) installed in the aircraft.

Q: The rules say that Battery Cells must be clearly labeled. Does this mean that each individual battery cell must be labeled?
A: If the cells are not labeled or are not visible we will accept an invoice clearly stating the cells used in the pack(s).

Q: Is it legal to mount the batteries on the exterior top surface of the fuselage?
A: No, batteries must be contained inside the aircraft surfaces.

Q: For the structural wing tip test, will the load be applied at the ends of winglets or other wingtip devices, or at the tip of the main span of the wing?
A: The lift point will be as far out the span of the wing as is possible.  See the FAQ for additional information.

Q: Can we create a micro-controller that will dynamically limit the throttle of our plane in order to remain under the 20 Amp limit?
A: No. You may not put anything between the Rx and the motor and/or any servo that will modify the PWM signal and may interfere with with the fail-safe.  You may use telemetry to notify the pilot of current draw.

Q: Would it be legal to intentionally cool the fuse before flying each mission?
A: No.  That would violate the "intent" of the rules.

Q: Is it legal to use tape  to secure our top hatch?
A: You may use tape for typical model aircraft functions such as holding hatches in place.

Q: Can we machine our own gearboxes or must they be commercially available?
A: You may make your own using commercial gears or may modify a commercial gearbox.

 

Mission Questions

Q: Can we use some type of dye or coloring to make the water more visible during mission 3?
A: No.  You may only use plain tap water.  Making the water plume visible should be part of your release system design.

Q: Does airplane need to have a fuselage during M1, could we put off the required fuselage for mission 2 and mission 3 during mission 1? For mission 2 and 3, are we allowed to add attachments to the fuselage which will carry the payloads?   
A: No.  Read the rules General section and FAQ Flight/Mission #2 and Aircraft #3..

Q: Does "flight weight" in mission 2 include the payload?  What about the empty weight?
A: Flight weight in mission 2 includes the passenger payload.  RAC for mission 2 does not include the passengers but does include all passenger accommodations.  RAC for mission 3 does not include the water but does include the water storage and release system.

Q: The rules state “The aircraft will enter the assembly area with the payload for mission 2 and 3 uninstalled.” Does this mean that the team must begin Mission 3 assembly with the entire TEIS (the specified payload for Mission 3) removed, or can components of the TEIS be installed in the aircraft before entering the assembly area?
A: The TEIS should be installed prior to entering the assembly area.  The water is the payload for mission #3, which will be filled in the assembly area.

Q: Do the passenger restraints need to be installed in the aircraft for mission #1 and #3?
A: Teams may decide if they want the passenger restraints (or portions) installed in the aircraft during Missions 1 or 3.

Q: May passenger restraints also serve as aircraft structural components?
A: No.

Q: In mission 3 must all of the water be dropped before the aircraft lands?
A: There is no requirement in the rules specifying how much water must be released.

Q: If all water is not released during the flight, will the RAC will be calculated with or without the residual water in the tank?
A: You may release any residual water that will self-exit the tank before the post-flight weight measurement

Q: The above question says that the residual water may self-exit the tank. Is it allowed to turn the aircraft such way that our trapped water will eventually will exit the tank?
A: You may command the exit valve open and tip the airplane but you may not tilt the aircraft beyond vertical in any plane (ie. can't turn it upside down).

Q: Are the teams responsible for providing the 2L of water or the 2L container that said payload is loaded into the aircraft from? If so, how will the volume be confirmed by the judges?
A: The organizers will have several 2L water bottles that will be used to fill the aircraft during tech inspection and during the pre-flight assembly period.

Q: May water be intentionally dropped upon or immediately after takeoff to reduce aircraft weight?
A: No.  The CAM device must be the only means by which water can be released and water must not be released until the CAM device senses the specified release altitude.

Q: In reference to the following passage from the rules regarding mission 3, “Single take-off and climb to 100 m altitude” There is no mention of completing laps for mission three. Are there flight pattern restrictions for mission 3?
A: The aircraft must complete a normal flight lap, the same as prescribed for other missions, and make a successful landing the same as any other mission.

Q: Does a propeller have to be installed on all motors during flight?
A: No.

Q: Can we change propellers/gear ratios between flights?
A: See the FAQ, you may change propellers.  If the aircraft and gearbox configuration is the same you may change gear ratios.

 

Aircraft Questions

General

Q:  If our team wants to use a 3D printer to print a part designed and modeled by the team, but the printer belongs to another organization, how much involvement from students would be required in the print process?
A:  See FAQ Aircraft Questions #4.

Q: Is adding/removing tape on the aircraft between missions allowed?
A: It depends what the tape is being used for.

Q: Is it possible to use two sets of wing that have different airfoil for different mission?
A: No, read the FAQ for details on allowable variable geometry.

Q: Are we allowed to use different battery packs for the different missions? To clarify, we do not mean a number of identical packs, rather that each pack contains a different number of batteries and different kind of battery cells as well.
A: Re-read the rules.  You may have different size/configuration/weight battery packs as long as all meet the rules (including battery type/chemistry) and all are presented, inspected and approved during the tech inspection.

Mission 2 Payload

Q: Can the passenger block be modified for weight reduction by drilling holes through the blocks?
A: No, you may not drill holes in the passengers.  Read the rules for what modification to the blocks is allowed.

Q: Is there a specification for the amount of chamfer/deburring allowed for the passenger block?
A: Read the rules for what modification to the blocks is allowed.  Any deburring, chamfering, or sanding beyond what is required for safe handling (ie. to remove sharp edges) is illegal and will result in a failed tech inspection.

Q: Can we attach velcro, screws or other items to the "passengers" to help hold them in the aircraft?
A: You may not make any modification to the passengers, including attachments, other than what is described in the rules.

Q: Can we use sticky tape or "tack it" on the floor and on the side wall and place the passengers on them?
A: As noted above, you can't glue/tape items to the passengers, that includes attaching the airplane to the passengers (or the passengers to the airplane).

Q: Should the spar box obey the 0.5" gap rule between an aluminum block or is 0.5" aft-fore rule just a matter for block placement?
A: The rules say "open space".  Note the comment in the rules on "seats"/mounting.

Q: the rules writes There must be at least 1/2" open space fore/aft around/between each passenger.  Are we allowed to select fore-aft or around-between or do we have to use both of them
A: You must meet all of the clearance requirements (all sides) as specified.

Q: For Mission 2, if the passengers were to be aligned in a single row which requires a 1" space to one side of the passengers totaling a in a 2" wide payload, this would cause a balancing issue. Is it allowed to stagger the passengers so that each passenger has 1" to the side of them but they are not technically in a row.
A: If the passengers "switch sides" in the aircraft then the 1" wide aisle must continue across between the passengers at the stagger.  Note also that the exclusion for spacing between a passenger and the side of the aircraft does NOT apply to the side(s) of a removable payload insert.

Q: For Mission 2, must the blocks be rigidly fixed within the aircraft or is some amount of movement/shifting allowed?
A: The payload must be sufficiently secured to prevent shifting during flight.  Payload integrity will be checked during the tech inspection.

Q: Must passengers stay restrained during landing?
A: They may not exit or damage the aircraft during landing.

Q: In the rules it is stated that "reasonable provisions for passenger "seats"/restraints may protrude within the specified open space area." I know that the restraints may not cover the blocks completely, but what is considered acceptable?
A: You may have no more than 2 x 1/4" tall contact points (per passenger side) between the passenger and the restraints to hold them in their location.  The passenger may however "sit" on the floor, seat or other platform on the bottom.

 

Mission 3 Payload

Q: Is locating the altimeter circuit in the fuselage aft of a tractor propeller considered intentionally placing the circuit in a region of low pressure?
A: Read the rules for information on pressure port requirements.  Being behind a propeller will not necessarily place the port in a "intentional" low pressure area.

Q: Does a downward-facing angled surface count as a bottom exterior surface? (i.e angled aft fuselage or angled wing tips)
A: This is too general to answer concisely, if you have a specific configuration question you may submit a Confidential question including the details (drawings) of your aircraft design and location.

Q: The mission description says, the release valve has to be servo operated. Is it correct to assume that as long as the release mechanism is actuated by a servo, the team can design any type of release mechanism such as a trap door or a plug type opening for the water release?
A: You can use any type of "valve" as long as it meets the actuation required in the rules.  Be sure to also read the requirements on water "loss" in the mission 3 section.

Q: As a water valve, may we use a form of a solenoid? Instead of having the CAM system control a servo, we would have it link to an electromagnet, opening and closing the valve.
A: The rules say the valve must be operated by a normal model servo.

Q: Can we attach a switch between the CAM and our time-end indicating system's servo? Our concern is that a long time will pass between the pre-tech and the actual flight (due to weather conditions or any other reasons) which will empty our battery.
A: You will need to develop an appropriate control system and process for the CAM to retain it's settings between when the system is armed in the assembly area and when your flight begins.

Q: Is there any restriction for the material and ingredient of water tank?
A: No, normal aircraft construction and materials are acceptable.  Note that collapsible/elastic tanks are considered "pressurized" and are not allowed.

Q: Are bladders included under the definition of "collapsible" water tanks?
A: Yes if they are flexible/elastic/collapsible or made from flexible/elastic/collapsible materials.  Any surface or component in contact with the water is considered part of the water tank.

Q: Could you please elaborate further on what constitutes a "flexible" material or define a thickness that would be considered "rigid"?
A: Material should be selected such that it is obvious to the tech inspectors if it qualifies, they have the final decision. If you are looking at a material (not your assembly) and when you take a piece and bend it and it springs back it is probably rigid.  If you hold a piece of the material vertical from the bottom and it folds over on it's own it is not rigid.

Q: Can plumbing for the water system other than the tank use flexible materials?
A: See above, the "tank" may not be flexible/elastic/collapsible.  Elements other than the tank including inlet/outlet plumbing may use flexible materials

Q: A "pitot" style vent has the potential to pressurize the water tank from the ram-air effect. Is this style of ventilation system still allowed?
A: The pitot vent is specifically allowed.  Vents should be constant diameter, not a "funnel" designed specifically to increase pressure.

Q: During the Tech Inspection, will the water be put in the aircraft for the wingtip test or can an equivalent weight be used?
A: During tech inspection teams will demonstrate that the aircraft can hold the required volume of water.  Since the water payload is the heaviest payload it will be used during the wing tip load test.

Q: Since the “Time End Indicating System” (TEIS) is considered a payload for mission three, does that mean that all required attributes of the TEIS, including the water tank, must be removable from (not built into) the aircraft structure?
A: Teams may decide if they want the TEIS (or portions) installed in the aircraft during Missions 1 or 2.

Q: Is the water tank allowed to be simply the outer surface of the fuselage, or must it be a separate structure?
A: As stated above, different elements of the TEIS may be either fixed or removable.

Q: Can teams use a funnel when pouring the 2L of water from the plastic bottle into the water tank? Would the funnel be considered part of the empty aircraft weight?
A: Teams may use "ground support" devices during the water loading.  Anything that remains with the aircraft during flight will be part of the aircraft empty weight.

Q: In the case of an aircraft configuration such as the Blended-Wing-Body, which does not have clear distinction between fuselage and wing, where must the CAM be placed?
A: As stated in the rules The aircraft must not be designed to intentionally create a low pressure area at the CAM device, which also means the CAM must not be placed in a location such that it sees a configuration created low pressure.