Preflight. No aircraft, no matter how well designed and constructed, can operate properly without proper maintenance. On the Venture two of the most important airframe considerations are the brakes and the landing gear shock struts, as both are critical to directional control on the runway. A frequent check of the brake reservoir and a look for leaks at the wheel cylinders is strongly recommended. And a part of every preflight should be a look at the amount of extension of the nose and main gear struts. The nose gear works well at 1.5 to 2.0 inches, the mains at about 0.5 inch. These numbers presume a loaded aircraft. Keep in mind that if the strut is under inflated the pressure therein may be inadequate to push the strut into the fully extended position, in which case the landing gear will not fit into the wheel well and something will get bent, broken, or burned out in the attempt at retraction. In this respect the Venture is no different from any other retractable gear aircraft.
Emergency gear extension system. The gas cylinders do weaken over time, and should be checked annually and replaced at regular intervals not to exceed five years. The T handle pull cable also requires lubrication annually, which is an item very often missed. The emergency gear extension system works, as several pilots can attest, but it only works when the gas cylinders are good and the T handles are free.
Air/Oil shock strut service. By virtue of the manner in which the landing gear shock struts are engineered and manufactured, none are absolutely leak proof and all require periodic attention. When service is necessary, always service with both oil and air. The common mistake is to use air alone, which changes the air/oil ratio and makes the strut more spongy in its operation. A spongy strut on one side will definitely make the Venture want to turn to the other side. Not a good situation.
Differential braking. On the runway, below about 40 knots indicated airspeed, directional control can only be maintained by differential braking. So, if one wants to stay on the runway, one must be sure that the hydraulic brake system is bullet proof. To most of us old-timers this means rigid aluminum lines where possible and Aeroquip quality flex lines where necessary. While nyloseal lines are cheap, light weight, easy to install, and have been included in all eight of the aircraft kits I have purchased, I have never used them. And in 5000 hours of homebuilt operation, directional control has never been in question.
Landing gear emergency extension release cable. The emergency landing gear extension for the Venture electric undercarriage via gas struts is very simple and it works well if properly maintained and properly used. Proper maintenance calls for the removal of the cable from its housing and lubrication the cable with white grease at each annual condition inspection. Any cable which shows chatter wear (grooving) must be replaced. Proper use involves slowing the aircraft way down (try for 80 knots indicated) before pulling the cable release. It works, as several Venture owners can attest. Also remember that a gas strut looses 3% of its initially manufactured force each year.
AIR/OIL SHOCK STRUT OPTIONAL UPGRADE
By now most of you have read the excellent article by Larry Wood in the May issue of KitPlanes Magazine. The article details the addressing of a long standing complaint among some pilots regarding the ground handling of the Venture, namely the sponginess of the main gear air/oil shock struts. This sponginess is usually observed when the aircraft is flown solo and the air/oil ratio in the strut has been loaded on the side of more air, as in the case of servicing the strut with air alone. This is a stunt which most of us have pulled at one time or another. There has also been some erroneous information out in the field to the effect of inflating the struts to 1.5 inches static, which really accentuated the spongy problem.
At any rate, the friendship between Larry Wood and Jim Griswold goes back a long way to the days when they were both competing in the Olympics in the Tornado class in sailing. On the basis of that friendship, Jim did the engineering for the air/oil ratio change, and Larry did the testing. Several other Venture pilots, including yours truly, got the drawings and made and installed the parts. Most of us felt that the tendency toward lateral tipping was much reduced.
The very last thing which NuVenture Aircraft would like to do would be to diminish the success of several high time Venture pilots who have accumulated thousands of hours of flight time with factory originalshock struts. And, mandatory change notices from any kit manufacturer should be kept to a minimum. So NuVenture Aircraft has labeled the kit to make the air/oil ratio change an optional upgrade. Optional because the successful high time pilot will see no need for it. Upgrade because some of us felt lateral stability on the ground was improved.
NuVenture Aircraft can send you the drawings and the instructions for free. You or your friendly local machine shop can make the parts. Or you can get the drawings, instructions, and parts ready to install from NuVenture Aircraft for $150.00. To keep the aircraft legal the kit should be installed by the holder of the builder-repairmanšs certificate, or by a licensed A and P mechanic.
This is one subject which needs some discussion. The Venture owner/pilot must be very careful here.
Consider this. The original Venture design team had a collective total of something like 130 years experience in aeronautical engineering. It is that experience which is behind the construction details of the aircraft. So unless you, the builder/pilot/owner have the credentials to legitimately over rule the design team, best that you leave things alone. Some of the disasters which have occurred in Venture operation can be traced to poorly executed changes in the design carried out by unqualified individuals.
During the construction phase it is legal (though not necessarily wise) for the builder to modify the the aircraft under construction in any way that he sees fit. Supposedly the success (or failure) of any such modification will become proven (or apparent) during the 25 hour test period required by the FAA. The aircraft is then "certified," albeit one off, as tested. If the builder actually constructed the aircraft, be it from plans or a kit, he is eligible to receive from the FAA a "Builder-Repairman" license for that one serial number of that one aircraft. Said license allows the builder to conduct and sign off the "Annual Condition Inspection," as well as to repair or rebuild the aircraft as required.
The holder of the Builder-Repairman license (or any properly licensed A and P mechanic) may also modify the aircraft after the initial 25 hour test period. If the operating limitations were written after the year 2000 only a test period and proper log book entry by the Builder-Repairmen are required. If the operating limitations were written before the year 2000 the FAA must be advised of the modification and an FAA representative will assign and monitor the test period.
If one did not build the aircraft but rather purchased it after the initial test period he can neither conduct the annual condition inspection nor modify the aircraft. He may do routine maintenance like oil and tire changes, cosmetic work, and the like.
All of the above is legally speaking, and three entities are concerned with legality, those being the FAA, your insurance company and investigators for opposing attorneys. Bottom line: if you want to modify your Venture make sure your work is thoroughly documented and is going to be accepted by the first two entities. Some individuals think that they can circumvent the problem by just keeping things out of the log books, but don't you believe it. The Feds don't much care, but you would be amazed at how deep the well qualified investigators for insurance companies and opposing attorneys dig in high dollar cases.
There has been some concern of late about the spring cartridges which are an integral part of the control system. Some Venture owners have concluded there is an error in the design. NuVenture Aircraft feels that rather there is a problem with maintenance concerning proper lubrication.
At each annual condition inspection the trim cartridges should be removed, disassembled, cleaned, and inspected for wear. Any worn parts must be replaced - - they are all very simple and dirt cheap. The cartridges are then reassembled WITH PROPER LUBRICATION (lubricate liberally with a high melting point white grease) and then reinstalled.
Careful attention should be given to the springs in the cartridges, particularly the spring in the elevator system. At least one fatal accident can be traced to having a spring in the elevator trim cartridge which was far too light -- about one third of the required spring tension. The rudder and aileron springs are less critical.
By the way, changing anything in the control system would be considered a major modification by the FAA. If you are not qualified as per above to make a major modification to your Venture, don't do it.
Nose Gear Scissors and Shimmy Damper
The original design team noted above did experiment with both nose gear scissors and shimmy damper, and I have pictures in the files of such arrangements. However, these ideas were rejected when the Venture design was frozen, and subsequently Ventures have flown thousands of hours without them. Now a couple of Venture owners have resurrected the idea.
It should be noted that one of those Venture owners incorporated the scissors and shimmy damper into the original building which, in accordance with the guidelines above, was perfectly legal. However, there is no "before installation" data to compare with "after installation" data so there is no way to know if indeed the modification has any value.
The other Venture which incorporated nose gear scissors and shimmy damper was modified by the purchaser of the aircraft. The aircraft had been flown by the purchaser for a number of hours before the scissors and damper were added. Shortly after the modification was added the pilot lost control of the aircraft on landing and the aircraft was destroyed in the resulting runway departure. The owner/pilot still thinks the idea is a good one, and attributes his own loss to poor execution of his good idea.
Increased Positive Castor
It should also be noted that in the latter case above another factor may have been much more important. The owner/pilot (who was not the initial builder) increased the static castor of the nose gear by increasing the length the nose gear retract link. Keep in mind the Venture, properly constructed and with properly inflated struts, exhibits 3 degrees of positive castor, which is about right for a tire rolling on the ground at 100 miles per hour. In theory, one might think that adding more castor would improve directional stability of the nose wheel. But in fact, the increased static castor added to the dynamic castor of the rolling nose wheel tire coupled with a "gentile lowering of the nose gear" (which greatly increases the castor angle at full nose strut extension) may have increased the total castor to a point of instability.
Those of us who are familiar with the early development of the Venture are aware that the first prototype Venture N62V exhibited quite a large amount of positive static castor. It should be recalled that the prototype aircraft also exhibited a violent shimmy problem. In other words, some castor is necessary, but at some point apparently too much positive castor in the nose gear of a Venture causes that nose gear to become unstable resulting in such a severe shimmy that directional control may become impossible. Questair addressed the situation by redesign with much less static castor (approximately 3 degrees) and froze the design at that number. Unless someone can prove with some really good experimentation that the 3 degrees number is incorrect, it should stay that way.
Another note about castor. In order for castor angle to do its job (that of causing the wheel to roll in the same direction as the mass to which the wheel is attached) the wheel must be carrying the weight of the engine above it. Proper castor is ineffective if the wheel is unloaded or very lightly loaded. This fact can be demonstrated with the common grocery cart whose two forward wheels obviously free castor. Note that when the cart is empty those two forward wheel readily shimmy. Now place two 24 can cubes of soda pop in the front of the grocery cart. The shimmy tendency disappears completely. Enough said.
Finally, one Venture was lost on landing due to negative castor, yes, NEGATIVE castor. The nose gear strut extension was 0.5 inch, and the main gear strut extension was 2.0 inches. When we set up this configuration on our Venture we measured a nose gear castor angle of 5 degrees negative, not 3 degrees positive. Those who have tried to pull a loaded wheel barrow backwards know that it can't be done with any degree of consistent success. Same with landing the Venture in question. When, on landing, the nose wheel was planted quickly enough the dynamic positive castor of the tire patch moving aft was able to exceed the static negative castor, so the tire rolled straight. If the nose came down slowly the nose wheel cocked and the Venture left the runway. Twice the pilot was able to power back into the air. Unfortunately, the third time was the charm, and the pilot proceeded to&nbs! p;dig up 100 yards of sagebrush. The pilot was fine, the Venture didn't fare so well.
A Fixed Gear Venture?
It has come to our attention that one individual who purchased a Venture has contracted to have a fixed tricycle gear installed on his aircraft. Naturally, NuVenture Aircraft is very much opposed to this type of pollution of a perfectly good aircraft.. The Venture in question features an engine from a Piper Malibu complete with turbochargers and in theory it could cruise at flight level 24 where the increased drag of the fixed gear is much less and is further offset by increased power output of the turbo charged engine.
Several question arise. Who is doing the engineering on this conversion? Is the individual performing the work qualified to do so as per the discussion above? Is the FAA involved? (They should be since the aircraft was built long before the year 2000.) Will any Insurance Company indemnify this conversion? Does the pilot really want to always be be on an IFR clearance and sucking on oxygen? Is two hours of flight endurance enough? And finally, what is the converted aircraft going to be called? It sure does not fit our description of a Venture anymore!
It is understood that the stimulus for this conversion was, in part, fear of runway departure on landing by individuals who have experienced same. While it is agreed that a pilot should never fly an aircraft of which he is afraid, we feel that the Venture is one aircraft which can never be made easy and simple enough for every pilot to fly. So those who can't land it should have a healthy respect for (read that as "be afraid of") it.
Factory Approved Modifications
NuVenture Aircraft has found the following modifications to the airframe to be desirable.
Change of the air/oil ratio in the landing gear shock struts. This has been noted earlier under the heading of maintenance and the factory has available at a very reasonable cost a kit to accomplish this change.
Separation of the nose gear steering and braking systems. Steering capacity of the nose gear is removed altogether and the nose gear is allowed to free castor. The vertical rod and bell crank must be retained to limit side to side travel. The bimba cylinder can be retained (it does not even need fluid in it) to produce some drag or resistance to turning, though the system has too much hysterisis for the bimba cylinder to constitute a shimmy damper action. Just remember that in order to turn the aircraft must be rolling forward at a reasonable speed.
The incorporation of AN quality hoses and fittings in the brake system. Since steering is via differential braking only the brake system has to be bullet proof. New kits are delivered with such hoses
The elimination of the sump tank. The sump tank contains two check valves and the failure of either can and has caused the loss of fuel flow to the engine. When the sump tank is removed provision must be made to return fuel vapor from the engine to the tank from which the fuel is being fed to the engine. This requires either two parallel valves or one stacked valve and a new return line to each tank. A number of Ventures are currently being flown with this configuration. New kits are being thus supplied.
Separation of flap and aileron function. The flap function can be easily separated from the aileron function to allow the flaps to be deployed separately. The flaps can be actuated either electrically or manually. Physically the control surfaces are still flaperons, but the functions are actuated separately. Bottom line: separation precludes uncontrollable roll due to a split flap condition.
The Venture is a piece of cake to fly. Control in pitch and roll axes is crisp and very solid and the heavy wing loading gives the impression of flying a much larger aircraft. And the thing crosses the land in seven league boots But like my first flight instructor said 50 years ago the only challenge in flying is in the few seconds when the aircraft returns to earth. Indeed, most Venture accidents have occurred in the course of landing. Any high performance aircraft like the Venture must be very precisely handled in all phases of flight, but particularly in maneuvering flight (flight near the ground.) Following are some things that work.
Apply throttle slowly so as to avoid P factor or torque effect. Some right brake may be necessary at the start of the take off roll. Rudder and aileron become effective around 40 knots. Use them. Accelerate to 80 knots and ROTATE BRISKLY. This allows rapid full extension of the nose strut and assures quick capture of the nose gear piston with the tire within 1 degree of center, which is exactly where you want it to be when you land.
Unless one is operating from a very long runway (where one could cut the power and land in case if an engine emergency) immediate gear retraction is a good idea so as to get rid of the landing gear drag. So what should the pilot watch for the next 10 seconds? THE AMP METER. Each landing gear motor has a maximum current draw of 5 to 6 amperes, so the amp meter should never show more than 10 to 12 amperes. If the amp meter shows more than that, stop the retraction cycle by pulling the 3 amp landing gear control circuit breaker. Then isolate the problem. This action can prevent burned out motors, bent up gear doors and a host of other problems.
While the gear is retracting or extending the warning light for each gear, main and nose, shows red, indicating an "in transit" condition. Again if a light fails to go out in 10 seconds or so again pull the breaker and sort out the problem. (Of course, two green lights indicate that the gear is down in the landing position.) The gear extension time takes the same 10 seconds and it is still a good idea to watch the amp meter like a hawk. Of course, emergency gear extension is always an option, but care and attention should always be give to the air pressure extension cylinders and the release cables as noted somewhere above. Also for the emergency gear down system to work the aircraft has to be slowed WAY down (to 80 knots or less) to reduce the slip stream air load which opposes extension.
While the red line for gear extension is 170 knots indicated, it is good practice to slow well below that before placing the switch in the down position. Unless one is following a jet airliner on a long straight in approach the slower speed of 130 knots is better for pattern entry anyway. Pattern speed of 100 knots is comfortable (remember two fatal Venture accidents have been due to departure stalls in the pattern. Over the fence at 80 knots works.
Now for the important part. As soon as the main gear tires are on solid LOWER THE NOSE TIRE PROMPTLY and keep it on the ground with forward stick pressure if necessary. The reason for this is found in the above discussion of castor. It is necessary that the nose tire be weighted in order for castor angle to do its job of keeping the nose tire rolling straight. One caution: don't anticipate the forward stick pressure and land on the nose wheel first. Don't laugh -- it has happened and the result was not pretty..
Recall that when the Venture touches down the aileron and rudder are still very effective down to a speed of about 40 knots so remember to continue to fly the aircraft. If you are operating into a short field, say 2000 feet, some heavy symmetrical braking will be required. Again, be careful about anticipating heavy braking -- more than one Venture pilot has ruined a tire (or two) by being on the brakes before touchdown. And yes -- a Venture roll out can be maintained straight with one main gear tire flat.
Keeping the fuel load balanced in the long wet wings of the Venture is not just a good idea, it is a "must do" situation. While the electric aileron trim can compensate for a heavy wing in the air, the landing gear shock struts are less able to do so on the ground. Switching fuel tanks every 30 minutes or 10 gallons of fuel flow does the trick. Flying solo from the left seat good practice would dictate carrying 5 to 10 gallons more fuel in the right tank at the point of landing.