18August2017

You are here: Home Articles Others Inverted Flat Spin World Record...Third Time is a Charm
Tuesday, 25 March 2014 21:07

Inverted Flat Spin World Record...Third Time is a Charm Featured

Written by  Ingrid Font / Spencer Suderman
Rate this item
(2 votes)
Spencer Suderman - Inverted Flat Spin small

81 turns of inverted flat spin was the new World Guinness Record achieved by American air show performer Spencer Suderman over the California desert flying his Pitts S-2B fully prepared for the occasion.

 

The previous world record holder was the stunt pilot Wayne Handley, who completed 78 rotations fifteen years ago. Suderman had tried to beat this record previously, but he failed in 2011 and 2013 with 64 and 77 turns respectively.

 

Spencer Suderman began his flying career while working on his Bachelor of Science degree in business at California State University Northridge in the late 1980's. He earned a private pilot's certificate, commercial rating, instrument rating, and then became a CFI (Certified Flight Instructor) in 2003. While working on his instrument rating in 2000, he went through a spin and unusual attitude training program.  This training teaches pilots what to do in emergencies and involves mild aerobatics.  Spencer soon discovered that aerobatics are amazingly fun and quickly lost interest in merely flying straight and level.  After attending numerous aerobatic contests in the Super Decathlon Spencer moved up to the high performance Pitts S-2B which launched his career as an air show pilot in 2006. Now he taught to train other pilots his Be-A-Safe-Pilot training offered through the Torgoen Academy.

In the following paragraphs Spencer Suderman explains in Snap&Roll the conclusions from his experience after breaking the Inverted Flat Spin World Record.

Spencer Suderman portrait
 Spencer Suderman portrait

On March 13, 2014 at 11:39 am PDT a new world record for most inverted flat spins performed in one attempt was set when 81 full turns were completed in a Pitts S-2B.  The old record of 78 turns was anything but easy to beat and it took 3 attempts over the California desert to do it.

This spin was entered at 23,000’ and the recovery initiated at 2,000’, 3 minutes and 15 seconds later  after which the plane returned to straight and level flight at 950’.  This flight and all of its preparations were a data driven exercise in the research and development of aircraft configuration, pilot performance, problem solving and most important; flight safety.

Flight Timeline:

10:39:24 Engine Start

10:52:21 Takeoff Clearance

10:52:33 Wheels Up

11:36:06 Rolled Inverted 23,000

11:36:15 Spin Entered 22,900

11:39:21 79th turn completed at 2600'!

11:39:27 Spin Recovery Initiated 2100'

11:39:30 Vertical Downline 1700'

11:39:38 Level Flight at 950'

11:45:48 Landing

History

Attempt #1

On March 10, 2011 after departing from the Naval Air Facility El Centro and climbing to 21,000’ then entering the spin at 20,500’ only 64 turns resulted. 

Attempt #2

On December 8, 2013 after departing from Naval Air Facility El Centro and climbing to 23,000’ an unsuccessful attempt was made to enter the spin which resulted in falling out of the insipient phase of the maneuver, recovering at 20,000’ then climbing back up to 22,000’ and entering the spin at 21,600’.  Only 77 turns resulted but this was still a big improvement from the previous attempt.

The gains in performance between the first 2 attempts were due purely to modifications on the engine and optimized tuning of the weight and balance of the plane for the intended purpose of the flight.  The improvement in performance between attempts 2 and 3 was purely about how the flight was managed and the control inputs to enter the spin.

Spencer Suderman 79th turn
79th turn

Understanding the Maneuver

While an in-depth discussion comparing and contrasting the different types of spins is beyond the scope of this article and has been written about in great detail by several other prolific pilots/authors, I will simply remind everyone that spins are either upright or inverted then normal or accelerated and possibly aggravated but in all cases other than an inverted or upright power-on flat spin the airplane is still flying since there is laminar flow over the wings and tail.  That is why a normal upright or inverted spin can be accelerated by using the elevator to decrease the angle of attack.  It is important to understand that during a power-on inverted flat spin the plane is not flying but it simply falling and rotating due to thrust from the propeller and there is no manipulation of the flight controls that will increase the rate of rotation but certain flight control positions will actually slow it down.  Of this fact I am certain because video documented tufting research performed during numerous inverted flat spins indicates that this is the case and emphasizes the importance of proper flight control positioning for maximum rate of spin.

The inverted flat spin is largely misunderstood by most aerobatic pilots as I have learned and requires a different way of thinking to understand what is happening and why.  The biggest “A HA!” moment for me came when I realized that the propeller drives the maneuver through asymmetric thrust about the Longitudinal axis (nose to tail) rather than gyroscopic precession as I had thought. 

When an airplane flies forward all of the propeller blades make thrust because the disk of the prop is mostly perpendicular to the airflow through the propeller.  During the inverted flat spin the airplane is falling on its back (i.e.: dropping towards the ground at 65mph at 5000’ agl) so the airflow is parallel to the disk of the propeller and, much like a helicopter in forward flight, one side of the disk has blades that are advancing into the airflow while the opposite side has blades that are retreating and approaching a condition known as “retreating blade stall”.  In effect they generate little or no thrust while the advancing blades generate most of the thrust which is what drives the maneuver and explains why you can only do an inverted flat spin with right rudder in a Lycoming powered airplane.  After much experimentation (spins recorded on video) with various prop settings and throttle position it became quite apparent that high RPM and full throttle with the fuel flow (mixture) set for best power 100° rich of peak provided the highest spin rates.

Anyone who spins airplanes should be extremely comfortable with how to recover from all types of spins using both a normal proactive method and an emergency method but it has been proven that either recovery methods are virtually foolproof and perfectly reliable in the Pitts when executed correctly.  PARE®  is the acronym for Power(off)-Aileron(neutral)-Rudder(opposite)-Elevator(to neutral) and is the normal proactive method that works particularly well on the recovery of inverted flat spins, which is important if you plan to recover low.

Having opened my air show performance with inverted flat spins for years that start at 4500’ with the recovery initiated at 2000’ I have learned to perform PARE® so quickly and precisely that I can go from a full power-on inverted flat spin to a vertical down line in 400’ then decide whether to pull out of that dive easy or hard as the situation calls for.  In trying to break the inverted flat spin world record I knew that after hanging inverted and spinning down at -1.5G (indicated on the G-meter) for upwards of 3 minutes would require an easy pull from the vertical after the recovery to avoid a high positive G excursion that would cause GLOC (G induced Loss Of Consciousness).

Spencer Suderman Ready-to-go
Spencer Suderman, ready to go

Formulating the Plan – Engine Improvements

After attempt #1 it was clear that in order to break the record I would need to start from a higher altitude and increase the rotation rate of the plane in the spin.  Since reliable information about making planes spin faster seemed elusive I turned my focus towards climbing higher.  Understanding that aerobatic planes in general and the Pitts in particular are not made for high altitude flight for a number of reasons starting with the symmetrical airfoil that is horrible at flying in thin air to a large number of other design features that work well for low altitude aerobatics but lose performance quickly as the air gets thin.  When you start asking around about how to increase the service ceiling of an airplane the answers seem to start with a discussion of increasing horsepower then move on to metal propellers with thin tips.  None of these options are available for a certified aerobatic plane that is trying to break a record for inverted flat spinning and may also have a loose nut in the cockpit connecting the seat to the stick ;-)

In the interests of leaving no possibility on the table around the metal vs composite prop question I went flying in an S-2B that has the original Hartzell 2 blade prop and learned that it spins ½ turn per 1000’ slower, documented with video of course, than an S-2B with the MT 3 blade composite prop, so that put the metal prop idea to rest.  This should come as no surprise since one of the many advantages of composite props in aerobatics is the lower gyroscopic rigidity in space due to the reduction in weight at the tips.

Now that I was focused on the engine I called the man who knows more than anyone about aviating in the highest flight levels in a small piston powered airplane; Bruce Bohannon.  Bruce holds many world records including the one I wanted to hear about the most; highest altitude (47,067') for a piston airplane in Class C1.b (takeoff weight between 1102# and 2201#).  We talked about twin turbos, nitrous oxide injection and all sorts of things that are almost  guaranteed to turn expensive machinery into a boat anchor within a few hours of assembling it but might be useful long enough to break a record.  Of course the airplane itself is still the wrong airframe for this type of flying but the right tool for the job of inverted flat spinning. 

As the conversation meandered through the possibilities we identified the biggest return on investment by advancing the magneto ignition timing from 25° btdc[1] to 40° btdc with the caveat that full power could only be applied after climbing through 10,000’ or the engine would detonate itself on takeoff.  The other consideration in this approach was managing the power on the rapid descent during the spin and that would have been the biggest challenge.  The other option would be electronic ignition with automatically variable timing but nothing was on the market at the time for the Lycoming IO-540 in a certified plane so I considered learning how to precisely and quickly readjust the magnetos on a regular basis.

Around this time in October of 2012 I read a press release from Electroair of Howell Michigan about developing an STC’d electronic ignition system for 6 cylinder Lycoming engines to complement the STC already obtained on their system for 4 cylinder engines.  I called the president of the company and told him my story, listened to his story and we decided to work together in a flight test program that was written about in the August 2013 edition of Sport Aerobatics (“Flight Level 220 in a Pitts”), the rest is literally history now!

Spencer Suderman landing
Landing

Formulating the Plan – Increasing Spin Rate

In early 2013 while waiting for delivery of the electronic ignition that was still a few months away I turned my efforts towards increasing the spin rate by tuning weight and balance.  Leaning heavily on my Drift Innovation HD video cameras I documented spin rates at various altitudes when flying alone and with a passenger in the front seat. 

Anyone who has ever calculated the W&B of a Pitts S-2B or S-2C with a normal size adult passenger in the front seat understands the unspoken truth about flight training in a Pitts and as it turns out the spin rates are faster with both seats occupied due to aft CG but that is also a lot of extra weight to try and drag up to altitude and frankly I’m not sure anyone else wants to go along for THAT ride.  After a fair amount of experimentation I figured out how to get the CG location to the aft edge of the envelope with minimal increase in weight and without sacrificing safety when it comes time to recover from the maneuver in the accustomed manner.

Once the W&B problem was solved I did a series of test flights in small blocks of altitude from very low to as high as practical in order to measure spin rates per 1000’ and build a spreadsheet model that could be used to predict through extrapolation the anticipated performance up to 23,000’ and make a go/no-go decision about another attempt at the record. 

My spreadsheet told me that if I could get to FL230 and make a clean entry with a crisp recovery at 2000’ that 83 turns would occur.  Given that 81.75 turns were recorded my calculations were only off by 1.5%.

 

Spencer Suderman climbing
Climbing

Formulating the Plan – Coordinating the Flight

In the middle of September 2013 I contacted my friends at NAF El Centro and asked about the possibility of using their air space in November to make attempt #2.  The mission of this Naval air facility is to accommodate fighter jets and attack helicopters for training activities on their bomb ranges and of course host the Blue Angels winter training so everyone there is spring loaded to say yes because this place is a “hotel” for aircraft and hospitality is everything.  Helicopter squadrons from the USMC, British, and Danish forces come to El Centro to train in brownout conditions caused by the native desert sand. 

My last attempt at breaking this record in 2011 was the same week as the annual air show so all of the accommodations are already in place for civilians and their aircraft to be on base.  After making my request to the base commanding officer it was approved for early December and I would have to arrange for my own fuel since avgas is nowhere to be found on a military base. 

On a side note, the only reason that the Navy let me land on their normally closed to the public airfield and use their restricted air space is because over the years that I have flown in their air show it was  demonstrated that my level of preparation, airmanship and safety consciousness is becoming of an air show professional.

As I coordinated my flight for December 8, 2013 the plan called for me to depart Camarillo airport on Saturday December 7th and first land at Imperial County Airport for fuel then make the final 5.5 mile leg to NAF El Centro, spend the night on base with my support crew and the official Judges along with the president of Electroair who all drove there on Saturday and make my attempt at 9:00am Sunday.

As often happens in GA the weather is the biggest factor in diverting the best laid plans and I wasn’t able to depart Camarillo airport on Saturday due to a severe wind event in El Centro.  Everyone was there but me and my airplane.  Plan “B” went into effect and I departed Camarillo at sunrise on Sunday which only delayed my record attempt flight in El Centro by a few hours.

After landing and reviewing the video only 77 turns were accomplished and given that the record was 78 it was astonishing that I could have such a near miss.  During the flight I accidently pulled the throttle part way off the wide open stop while making a mixture adjustment and didn’t notice the change in noise levels because my ears were clogged from the rapid pressure change.  I spun for nearly 4000’ at half throttle which cost me the record that day.  Upon close study of the videos, there were other mistakes made as well which were taken as lessons learned for the next attempt.

At this point there was no doubt in my mind that the plane could break the record IF the pilot doesn’t prevent it from doing so.

With my tail between my legs and my ego crushed I sheepishly went to the commanding officer and public affairs officer of the base and thanked them for their support and asked for 1 more chance right before the air show in March, which I was already confirmed to perform in. Without even blinking they said yes and I ended the year on an uptick.

Spencer Suderman after landing
Spencer Suderman after landing

The Last Chance

I figured that my third attempt to break this record in El Centro would probably be my last because after a while your credibility wears pretty thin when you don’t do what you say and I really felt like I owed them a world record for all they have done for me over the years.  I spent the next several months making sure that everything was dialed in: I practiced entering the maneuver with enhanced in-spin aileron to assure that all flight controls are engaged especially in the high altitude and practiced crisp recoveries with an easy low G pull.  I spent more time riding my bike and doing squats to build leg strength to keep that right rudder all the way in for 3 minutes.  I serviced the oxygen mask, tank and regulator to make sure they were all in perfect working condition and ran multiple tests on all 3 cameras letting them record until the batteries ran out of juice to assure that 3 hours of video could be captured which is the expected length of a battery charge.  The Garmin Foretrex 401 GPS with barometric altimeter to record descent rates and get me right over my “SPIN” waypoint was checked on every practice flight, if any piece of equipment needed to fly safely or document the event wasn’t up to the task it was going to be replaced.

For this flight El Centro had reserved restricted area R2510A which only goes up to 15,000’ for air show week so I had to coordinate ahead of time with LA Center for clearance into the class A above that.  Working with LA Center was the easiest part of this process since I already knew the ins and outs of taking a VFR airplane into class A airspace and all of the same people were there since my last attempt.

I arrived in El Centro on Wednesday March 12, 2013 and prepared the plane for a 9:00am departure on Thursday morning.  When the sun rose so did multiple cloud layers over the area so that delayed my takeoff for nearly 2 hours while waiting for it to clear.  As every GA pilot knows there is nothing more frustrating than waiting for weather to clear for a flight that you HAVE to make.  It was worth the wait because anything that could obscure the vision of the cameras and cast doubt on what needed to be documented would have ruined the day.

I welcome all challengers to my record and give this advice:  You will need to find a way to climb higher and spin faster.  Keep in mind that the plane rotates at a constant rate but falls quicker in the higher altitudes due to the thinner air; my average number of spins per 1000’ was 3.93 and the plane achieves 5.6 turns per 1000’ in the last few thousand feet before the recovery.   Here is the data on vertical speed from this flight:

Descent Rates:

21,000' 8900 feet per minute

16,000' 8100 feet per minute

11,000' 6800 feet per minute

6,000' 5600 feet per minute

Good Luck!

Spencer Suderman looked the big moment
                                               Spencer Suderman looked the big moment

 


[1] In a reciprocating engine, top dead center of piston #1 is the datum point from which ignition system measurements are made and the firing order is determined. For example, ignition timing is normally specified as degrees before top dead center (BTDC).

Read 37661 times Last modified on Monday, 06 March 2017 08:49
Login to post comments
"Aerobatics is the hidden rythm of our soul..."

Newsletter