Cherokee takeoff
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I bet everyone who watched Top Gun: Maverick scoffed at the scene where Maverick sheds his stolen F-14’s nosewheel on a “50-foot obstacle” while attempting a short field takeoff… from a taxiway. In Mav’s defense, Tomcats don’t have an approved Short Field Takeoff procedure—that doesn’t involve a catapult. However, folks flying light GA aircraft don’t have that excuse. There’s lots of guidance out there designed to keep us out of trouble. Problems arise when we don’t comply with it, and the results can be catastrophic.

So, let’s do a shallow dive into what’s required to execute a successful “high performance” takeoff. We’ll explore issues and confusion surrounding aircraft performance speeds (“V-speeds”) and flap use during takeoffs. We’ll discuss why it’s important to know exactly what’s required for your plane, and why you should always read the fine print.

There are exceptions to everything in aviation. Obviously, not all airplanes have flaps; we’re not addressing them here.

For brevity: I’m using “Pilot Operating Handbook” (POH) to include all the various aircraft documents, including the Airplane Flight Manual, Pilot’s Information Manual, Owner’s Manual, etc.

Where to start?


The runway is soft and short—what speed should you fly?

When departing short, soft, and/or obstructed runways, there are two questions you must answer: What speeds do I fly, and are flaps required?

First, let’s review some definitions and generally accepted truths concerning V-speeds, flaps, and climb performance-related stuff:

  • Vx is best angle-of-climb speed. It produces the greatest altitude gain in a given horizontal distance. Vx is a function of excess thrust: the IAS for Vx increases with altitude. Vx is typically flown in a clean, no-flap configuration (there are exceptions).
  • Vy is best rate-of-climb speed. It produces the greatest altitude gain in a given time. Vy is a function of excess power: the IAS for Vy decreases with altitude. Vy is always flown in a clean, no-flap configuration.
  • Some airplanes have a published obstacle clearance speed (OCS). This speed is usually slower than Vx and is flown with approved flap settings. One notable exception: Cessna 150.
  • Even if the term “obstacle clearance speed” isn’t used, any speed other than Vx that’s directed for use until all obstacles are clear is an OCS.
  • If a flap-equipped plane doesn’t have a published OCS, it’s because flaps use isn’t approved for takeoff. In that case, any OCS should be the same as Vx.
  • Cessna usually publishes an OCS, along with a flaps-up Vx.
  • Piper doesn’t publish a separate OCS. They use a flaps-down Vx, followed by a transition to a flaps-up Vx after the obstacle has been cleared.
  • All flaps produce lift and drag. At some point, drag wins—usually around 10-20 degrees of extension (25 for Piper). The manufacturer will always specify the maximum flap setting approved, or recommended, for takeoff.
  • Some airplanes use flaps for short field takeoffs; many don’t.
  • All airplanes use flaps for soft field takeoffs—except Beechcraft.

It’s critical that pilots correctly interpret the manufacturer’s guidance on where, when, and how to transition through the various V-speeds. Using Vy—when airborne, clear of obstacles, cleaned up, and prior to establishing a cruise climb—isn’t that controversial. The confusion and creativity involve what happens from brake release up until that point.

Where to look?

POH chart

The performance section of the POH often includes important notes.

In most POHs, V-speeds and flaps are addressed in at least two places: the takeoff and normal procedures sections. A third place to check is the takeoff performance charts; they may have asterisk items that aren’t covered elsewhere in the POH. For example, the Beechcraft C-23 Sundowner takeoff checklist just directs “flaps—set.” It only adds “flaps—up” as a note on the hard surface and grass runway takeoff performance charts, along with an “at 50 feet” speed of 74 KIAS. The C-23’s 69 KIAS Vx is never mentioned.

Apparently, Beechcraft doesn’t want you to takeoff unless you can fly a normal climb profile.

Published procedures may be based on climb speeds, configurations, and profiles that you’re not used to; and may include steps for transitioning from an OCS though Vx, to Vy, etc., that are different than expected. Sometimes you must figure these out yourself, based on whichever “standard scenario” you’re facing: Short or soft field with/without obstacles; or the most challenging—a short, soft field with an obstacle.

When is Vx not Vx? Obstacle clearance speed vs. Vx

Isn’t clearing an obstacle what Vx is for? Why have an OCS that is slower than Vx?

The reason is simple: flaps help get you airborne quicker, however, they create a significant amount of parasite drag and a lower speed is needed to minimize this. Continuing to climb unnecessarily at OCS, with flaps down, is self-defeating. Since drag quadruples as speed doubles, getting the flaps up as soon as they aren’t needed is critical. That means transitioning (i.e., accelerating) as soon as it’s safe, to Vx, Vy, or something even faster.

Flying precisely is important, but…

Vx and Vy are usually far enough apart (10-12 KIAS +/-) that there’s a definite pitch change between the two. Sometimes OCS and Vx are also far enough apart (5-7 KIAS +/-) that a pitch change is required.

They can also be annoyingly close. The Cessna Skycatcher has a 55 KIAS OCS and 57 KIAS Vx. That 2 KIAS difference is difficult to fine tune even with its almost-too-accurate Garmin G300 digital airspeed indicator. The temptation to focus inside and nail it has to be balanced with the need to look outside—especially when you’re 12-15 degrees nose-high.

For short fields, the Skycatcher POH directs a climb at the flaps-down (one notch/10 degrees) OCS until clear of the obstacle, then retract the flaps when you’re faster than 60 KIAS. Confusion can set in because Vx is 57 KIAS… you’ve already blown through that, and in fact, operating at Vx is never mentioned anywhere else in the POH.

Conversely, the Cessna 150M POH directs a flaps-up 60 KIAS OCS, then states “If enroute terrains dictates the use of a steep climb angle, climb at a Vx of 56 KIAS with flaps up and full throttle.” In this case, OCS is faster than Vx, and both are flown clean—a rare case of slowing down after you’ve cleared the obstacle.

The concept of an “enroute Vx,” is unique to Cessna; other manufacturers address Vx in reference to takeoffs only. The 150M POH also refers to both a “climb speed” and OCS.

You’re supposed to decide whether climb speed means Vx or something else.

Climbing out at Vx: when is high enough high enough?

182 in climb

It is possible to climb too steeply.

The 1975 Cessna 185’s Maximum Performance Takeoff checklist states: “Climb speed—64 MPH until all obstacles are clear,” then retract the 20 degrees of flaps and pick up either a normal climb (110-120 MPH), or a maximum performance climb (101 MPH at Sea Level, to 94 MPH at 10,000 feet).

Then in the Enroute Climb section it states: “If an obstruction ahead requires a steep climb angle, Vx should be used with flaps up and maximum power. This speed is 86 MPH at sea level, increasing to 88 MPH at 10,000 feet above Sea Level.”

But if there isn’t an actual obstacle out there, what kind of climb profile should you fly… especially if you’re burning 24 GPH at maximum power?

My Tacoma-area airport has a departure which takes you immediately over the very-cold Puget Sound. One local C-185 driver likes to climb using that Maximum Performance Takeoff checklist (I’m assuming; based on his pitch attitude, 20-degrees of flaps, and the scream of near-supersonic tip speeds) until he’s high enough to glide to Portland… 101 nm away. Now, I don’t own a 185, but I’m thinking that’s a bit excessive.

As we’ve seen, Cessna provides unequivocal guidance on using Vx for situations other than takeoff, including some discussion about the drawbacks of doing so. For example, a C-150M POH note says: “Steep climbs at low airspeed should be of short duration to allow improved engine cooling.” Unfortunately, this note doesn’t point to all the other reasons to avoid unnecessary, extended climb-outs at Vx: overall engine stress, higher fuel burn rates, reduced forward visibility, higher AOA, higher drag, slower airspeed, closer to stall… more annoyed, noise-sensitive neighbors.

But what about engine failures after takeoff?

Worried about that “impossible turn”? Most pilots could make it back to the field if they at least reach traffic pattern altitude (TPA) somewhere close to the airport. As advertised, Vy will get you there quicker, however, it takes you further from the runway. But how much further?

The horizontal distance traveled between Vx and Vy while climbing to a 1,000 ft. AGL TPA is negligible; it’s going to be hundreds of feet, not miles. However, if you can’t hold Vx or Vy within +/- 10 KIAS, all bets are off.

To convince yourself, take a look in William Kershner’s 2006 Flight Instructor Manual, 4th Edition. There’s a chart (Figure 11-10, p.170) for a “Fictitious Airplane” that illustrates the relatively minor differences when operating at Vx versus Vy.

It shows that a 74 KIAS Vx climb yields a rate of climb (ROC) of 1,250 fpm and a 90 KIAS Vy ROC of 1,380 fpm. That’s a difference of only 130 fpm. If Vx was faster and/or Vy was slower, the ROC gap would be smaller; that happens as altitude increases. In this case, if you climb straight ahead for one minute, you’d be roughly 130 feet higher using Vy, and a bit further from the runway. If you stopped at a 1,000 ft. TPA, instead of flying for one minute, the distance would be even smaller.

Those numbers may seem excessive to pilots who are used to 500-600 fpm ROCs, not 1,000+ fpm, and differences between Vx and Vy of 8-10 KIAS, not 16-18 KIAS. But the spatial/lateral relationships remain the same. Obviously, your mileage may vary; that’s why it’s important to have an idea of what they really are in your plane. Instead of drawing charts and doing actual trigonometry, conduct your own flight test.

Still concerned about an emergency return? A better tactic might be to climb at OCS or Vx until all obstacles are clear, then circle near the airport at Vy until you reach a comfortable cruising altitude.

Tactics, techniques and procedures

Flap switch

Do flaps help or hurt? It depends…

There is no universal short or soft field procedure that always works for ever airplane.

Defaulting to a one-size-fits-all technique of extending one notch of flaps, holding the brakes… or letting her roll, running her up to max power, releasing brakes, rotating as appropriate, pitching up to hit that speed at 50 feet… or to hold OCS… or Vx, until clear of the obstacle, retract the flaps, climb out at Vx… or Vy… might work great most of the time. Or you might end up bending something.

Taking off with the wrong flap setting, either too much or not enough, is self-critiquing.

I once went “a notch too far” with the Johnson bar in my 1953 C-170B while attempting a takeoff on skis from a Fairbanks-area strip. The extra flaps added enough drag that I could barely crawl out of ground effect. Fortunately, I figured it out just in time so that the spruce trees in my flight path only barely scraped my F. Atlee Dodge skis as I clawed for a few more feet.

If you’re operating out of real soft fields—mud, icy slush, loose gravel, sand, wet grass, hot asphalt, etc.—then you’re a test pilot. Manufacturers may offer soft field techniques, but they won’t provide any data that supports your decision to try it. Although they might provide data for a hard dry grass runway, it’s based on adjustments to their hard paved runway calculations. For example, in fine print at the bottom of the Cessna 185 takeoff data chart for Takeoff Distance w/20 Degrees Flaps from a Hard Surface Runway, is the following:

Note 2: For operations on a dry grass runway, increase distances (both “ground run”and “total to clear a 50 ft. obstacle”) by 6% of the “total to clear 50 ft obstacle” figure.

Manufacturer guidance on speeds, flaps, and piloting techniques is all over the map. Not just between companies, but among product lines—even for the same airplane, depending on model year. It can get confusing and dangerous if you don’t pay attention.

There are gotchas when flying different planes from the same builder. For older 172s (mid-50s through early 70s), Cessna states: “To climb over an obstacle after takeoff use the Best Angle of Climb Speed of 60 mph, with full throttle and flaps up.”

The 1975 Cessna Skyhawk Owner’s Manual directs a maximum performance takeoff configuration of “Wing Flaps—UP” and “Climb Speed—68 mph (until all obstacles are cleared).” It then states: “If 10 degrees of flaps are used for minimum ground runs, it’s preferable to leave them extended rather than retract them in the climb to the obstacle. In this case, use an obstacle clearance speed of 65 mph.” An actual Vx is never mentioned.

There are significant differences between a 1956 C-172 with a 145 hp O-300 and a 1975 Skyhawk with a 150 hp O-320; don’t assume they fly the same and get ambushed by muscle memory.

Even the illustration of a generic high wing aircraft doing a short field takeoff in the FAA Airplane Flying Handbook is misleading:

FAA diagram

(Source: FAA-H-8083-3C; Figure 6-8)

In fact, newer Cessnas use OCS with flaps, then transition to a flaps-up Vx—maybe the FAA should have depicted a Piper instead?

On the other hand, if you fly PA-18-150 Super Cubs, the POH simply says, “FLAPS… Whatever.”

Before you shove the throttle forward and release brakes…

  • Always read the fine print so you have all the info needed to engineer your departure.
  • Fly airspeeds as accurately as possible, without staring inside at the airspeed indicator.
  • Know exactly what you’re going to do with pitch, power, and flaps.
  • Know what procedure is needed to clear that 50-foot obstacle off the end of the runway.
  • Determine what actual ROC you’ll need to clear any obstacles, whether you fly OCS, Vx, or Vy.
  • Finally, have an out in case it’s not looking good. I wouldn’t want “missed it by that much!” on my headstone.
Tom Curran
Latest posts by Tom Curran (see all)
22 replies
  1. John M
    John M says:

    Excellent article, which had me re-reviewing my POH with a more attention to detail. I had committed to memory Vx (81) and Vy (95), but now picked up on the nuances in the checklist and the Takeoff Performance sections of the POH. The takeoff checklist advises flaps 10* with rotation at 65 KIAS and initial climb at 75 KIAS. The Takeoff Performance section refines this and provides a liftoff speed of 63-71 KIAS and a “Clear 50 ft” speed of 69-78 KIAS (both weight dependent ranges).

    Thanks to your article, I now recognize the “clear 50 ft” speed in the takeoff performance charts as an OCS, and I now understand why Vx (clean) isn’t the best speed for obstacle clearance (flaps 10*).

    • Tom C
      Tom C says:

      Hi John,

      Thank you for the kind words. The goal was to hopefully get folks back “in the books” and thinking about how they operate their airplanes.

      In truth, the original version was twice this long; I cut it in half ….and I didn’t do a very elegant job.

      But, I’m glad it helped you and I appreciate AFJ for putting it out!

      Tom C.

  2. Eric E.
    Eric E. says:

    “All airplanes use flaps for soft field takeoffs—except Beechcraft.”

    Well my Beech T-34A USAF flight manual says to use 75% flaps for minimum run and obstacle clearance takeoffs. I do this frequently on grass runways, dry, wet, and snow covered.

    • Tom Curran
      Tom Curran says:

      Hi Eric,

      You got me on that one–I never thought of looking up something that old! I’ll plead “ignorance” and hide behind my “There are exceptions to everything in aviation” caveat.


    • Tom Curran
      Tom Curran says:

      Hi John;

      …a great point! (And part of the article I cut out.)

      The Archer III POH is a good example of how some manufacturers try to “describe” how to use an obstacle clearance speed, without actually calling it an “OCS”, and/or listing it somewhere along with the other performance speeds.

      A ‘gotcha’ with Archer models is the requirement that you figure out what that OCS really is; ”Accelerate to 60 knots…depending on aircraft weight”. So…what is the formula for that?

      Another trap could be the changes between the Archer II and the Archer III… and a good reason why you should always read the “Expanded” sections and not just rely on the “Checklist” .

      There’re some subtle(?) differences between what is printed in their respective Chapter 4 “Short Field, Obstacle Clearance” checklists, and how they are described in the expanded “Short Field Techniques” sections. They pretty match until you’ve “broken ground” ….

      The Archer III checklist then says:
      “Accelerate to best flaps up angle of climb speed-64 knots.”
      “Flaps…retract slowly (obstacle cleared & safe altitude).”

      The expanded section then clarifies:
      “After liftoff, control the airplane attitude to accelerate to 60 knots, depending on aircraft weight, passing through the 50-foot obstacle height. Once clear of the obstacle, accelerate to the best flaps up angle of climb speed of 64 knots while retracting the flaps…”

      The Archer II checklist says:
      “Accelerate to best flaps up angle of climb speed – 64 KTS lAS.”
      “Slowly retract the flaps and climb past the obstacle.”

      The expanded section then clarifies:
      “After breaking ground, accelerate to 45 to 54 KTS lAS, depending on aircraft weight. Continue to climb while accelerating to the flaps-up rate of climb speed, 76 KTS lAS if no obstacle is present or 64 KTS lAS if obstacle clearance is a consideration. Slowly retract the flaps while climbing out…”

      My points:
      – If you only referred to the “Checklist”, would it be unequivocally clear on when to raise the flaps?
      – Is “Slowly retract the flaps and climb past the obstacle” the same thing as “Slowly retract the flaps while climbing out…”?
      – The Archer II and III are not the same airplane; but are good examples of where you might be ambushed by negative transfer of “muscle memory”.

      Key Takeaway:
      As you pointed out; there might be an OCS described somewhere in your books–make sure you know how it ‘works’ for your plane.


  3. Stephen
    Stephen says:

    I finally understand now why the POH for the PA-28-161 says to “(Short Field) …maintain 44-57 KIAS (depending on weight) past obstacle” and “(Soft Field) Accelerate just above the ground to 52 KIAS to climb past obstacle clearance height” instead of using Vx (63kts). It is because the POH is giving us the airplane’s OCS without telling us it is giving us the airplane’s OCS. I instinctively understood the reasoning (even better after putting it into practice and seeing the climb) but never equated it to an actual “published” speed.

    • Tom Curran
      Tom Curran says:

      Hi Wil:

      I do not, although I hear lots of techniques discussed for Bonanzas. Maybe an experienced V-35 or A-36 Driver can add some wisdom/guidance here?

      (Are you a member of the American Bonanza Society/ABS?)

      Beechcraft/Raytheon’s POH guidance is kind of sparse when it comes to flap usage, compared to everyone else.

      For Bonanza V35, V35A & V35B; the POH (with revisions thru @ 1994) Section IV, Normal Procedures, BEFORE TAKEOFF checklist shows:

      11. Flaps… CHECK OPERATION, THEN UP.

      Then, on the single Section V, Take-Off Distance performance chart, it notes “Flaps UP” with no additional notes/caveats on runway surface, grade, condition, etc.

      Interesting, too, is that under “Airspeeds For Safe Operation”, it lists a “Lift-off speed” of 71 kts, and a “50 FT” speed of 77 kts. Then under “Maximum Climb”, it shows that the “50-foot” speed is actually “Best Angle (Vx)…77 kts” (again, no flap).

      On that note; like all airplanes, be cognizant of year-to-year changes for the same make/model.

      For example, in the 1982 A-36 Bonanza POH (with revisions thru @ 1994) both the BEFORE TAKEOFF checklist and single Take-Off Distance performance chart only show “FLAPS….UP.” The performance chart also includes the Note: “Runway… Paved Level Dry Surface”.

      OTOH, the 2002 A-36 Bonanza POH (with revisions thru @ 2006) includes a single BEFORE TAKEOFF checklist and two Take-Off Distance performance charts, one for flaps up and one for flaps down (“Approach” setting).

      The BEFORE TAKEOFF checklist shows:


      But you have to look at the “Take-Off Distance – Flaps Approach” performance chart for additional guidance. It directs: “Flaps…. APPROACH (BLUE)”. (“BLUE” alluding to the blue “Approach” setting light in the cockpit.) It also includes the note: “Runway… Paved Level Dry Surface”.

      There is no additional POH wording on when to raise the flaps in the subsequent TAKEOFF or CLIMB checklists; assume it’s when “clear of the obstacle”.


  4. T Boyle
    T Boyle says:

    Very good article, but I feel there’s are overarching questions pilots should ask themselves, if this level of takeoff precision is ever actually required: “What on earth are you doing? How did you get yourself into this situation? How can you ensure you never, ever again need to look up this section of the POH?”
    Because if you really need to know the difference between Vx and Vy, never mind the difference between Vx and OCS, you are deep into a situation of needing superior skill to overcome a lack of sound judgment.

    • Tom Curran
      Tom Curran says:

      Good points…

      If you get a chance, please take a look at one of my earlier AFJ articles: “Always read the fine print” (2019).


    • John M
      John M says:

      You assert the need to dig deeply into the performance section of the POH is the result of getting in to a bad situation caused by poor judgement. I submit this performance information helps ensure safety by avoiding the erosion of safety margins.

      In aviation, we tend to measure with a caliper, mark with a crayon, and cut with an axe. With respect to takeoff performance, POH performance data, runway lengths to the nearest foot, and ASOS weather are our calipers. From there, we introduce unknowns: Exactly what is our gross weight? How accurate is our airspeed indicator at the bottom of the scale? Are the tires inflated to spec? Are the engine and prop in like-new condition? That’s our crayon mark. Then we add in pilot performance: rate and accuracy of rotation, nailing target airspeeds, and being perfectly coordinated. Most pilots, like axe men, aren’t perfectly precise.

      To your point, I agree we should not be operating on the edges of aircraft performance capabilities. My POH provides caliper-precise numbers for ground roll and 50-ft obstacle clearance under specified conditions. The shortest runway I’ll accept is 1.5x ground roll, with 1.5x the 50′ obstacle clearance distance before the tree line. That buffer, intended to protect me from the crayon-mark unknowns and a certain amount of imperfect technique, keeps me away from the margins and within my own comfort zone.

      In order to retain as much of that buffer as I can, I want to achieve the best performance possible. This means flying the correct airspeed, which requires knowing the numbers and applications for Vy, Vx, and–now that I’ve read Mr. Curran’s article–OCS. Digging in to the performance section of my POH and using the airspeeds on which book performance is based keeps my safety buffer from being eroded by imperfect axe handling. So the pilot who consults the performance section of the POH and who employs maximum performance airspeeds isn’t necessarily in a bad situation caused by poor judgement. On the contrary, they may be seeking to fly with as much precision as possible so that safety factors they have built in aren’t needlessly eroded.

  5. Glenn Ingram
    Glenn Ingram says:

    I’ve been instructing for 40 years and teach the aerodynamics/ airspeeds for short & soft field T&L’s but have yet to see a pilot or Airspeed Indicator that can discern the small differences between Vx and OCS on the the fly. The airplane accelerates so quickly from rotation to Vx/OCS that most pilots are happy to be within 5 kts. of planned A/S. The width of the A/S indicator needle alone covers 2-3 knots. The key is establishing the right pitch attitude (8-10 degrees pitch up) holding enough right rudder to control yaw, then airspeed takes care of itself. Power is always “full power as indicated by the tach/MP”. My point is, there isn’t time for all this tweaking in a real world situation. Don’t hit the obstacle, smoothly transition to Vy and practice, practice, practice.

  6. Bob S
    Bob S says:

    Hi Tom. On short field operations the books do not always tell all.
    For instance if there is no obstacle, what ever happened to the 50/70 rule. Plus what is the most useless thing in one of these performances take offs. Not using the full length of the runway. Plus POH’s are great except they were produced by highly skilled test pilots in brand new aeroplanes. In many ways the POH’s are used as a sales tool.
    They should be used only as a yardstick to compare.
    Seaplane drivers prefer no flap TO’s in tight spots and then deploy 10*flap to lift off.
    My estimation is to have the aeroplane as clean as possible during the early stages of the TO to be able to accelerate to VX ASAP. Then apply 10* flap. Climb until all obstacles are cleared at VX. Lower the nose an accelerate to VY. Once above 200’AGL retract flap and proceed.
    Again TO weight is a determining factor as TO surface, headwind, and age of the aeroplane.

    • Wilcox Charles
      Wilcox Charles says:

      Bob, may I suggest that not using the full length of the available runway is not a POH issue but rather a pilotage and training problem.
      And while the POH data may be the product of testing by highly skilled test pilots, the data is reduced and expanded by performance engineers with factors added in the “normalize” the performance numbers to an average pilot. When you use “rule of thumb”, hangar- flying techniques, or other deviations from the POH, the you are now the test pilot. And unfortunately, probably not a pilot with a test pilot’s skill set or experience.
      Fortunately, in a Certficated Airplane, the test pilots have defined the flight envelope to keep the average pilot & passengers safe and the aircraft is tolerant to some degree of human error.

  7. Mike Heberling
    Mike Heberling says:

    Great detailed, comprehensive article. Like to speak to the subject of the takeoff roll.

    Soft Field: Rotate asap to 5 -10 degree attitude. Hold that AOA until liftoff and transition to Vx / Vy.
    Hard Surface: Rotate at bottom of white arc on ASI to 5-10 degree attitude. Hold that AOA until liftoff and transition to Vx/Vy. This is my normal takeoff on hard surfaces in all single-engine airplanes.
    During takeoff roll rotate to 10 degrees for no flaps takeoff and less than ten degrees for flaps extended takeoff. There is no dramatic pitch change when transitioning from liftoff to Vx/Vy.

  8. Ian Holliingsworth
    Ian Holliingsworth says:

    Nice article, Tom. As a highly experienced “bush” pilot (Cessna 180s and 185s) I would add one thought.
    My Flaps 20 climb-out might be at a slightly flatter climb gradient, but if it starts earlier in the run, it can clear an obstacle that accelerating to Vx would not permit.

  9. Wilcox Charles
    Wilcox Charles says:

    Nice article Tom and concur with the need to get pilots heads back in the books. I wish instructors would look at AC23-8 (and related regs) and introduce it to their students so the can understand where the POH/AFM data comes from. There are legitimate reasons to fly by the numbers and consequences if you don’t.

  10. Tom Curran
    Tom Curran says:

    I want to Thank You All for the comments (so far….); I appreciate your feedback!

    A couple more notes concerning “techniques” and obstacle clearance speeds:

    The goal of this article was to get folks thinking about how they “do stuff” in their airplanes, while reminding everyone that the primary source of how to fly their airplane has to be the manufacturer.

    Specific steps published in a POH/AFM are considered “procedures”. Regardless, I’ll bet everyone, at some point, has copied, adapted, or developed their own techniques. Then based on their experience, they continued to use them, in lieu of that manufacturer’s guidance.

    Not saying they don’t work…usually. A lot of us fly/have flown planes that are so old, there was NO printed “manufacturer guidance” available, that covered everything you could do in the plane. Flying planes like that requires a firm grip on the “fundamentals” of flying… the art and science …. and applying them appropriately.

    Some techniques are popular, albeit sometimes controversial, like starting a takeoff with flaps up, then “deploying” them while accelerating during the takeoff roll. Works on wheels and (as previously noted in the Comments) on floats (I’ve done it too) … depending on how/when/where you do it.

    But unless there’s at least a discussion, a checklist, or a table/graph, etc., that addresses it in a POH/AFM, you are the proverbial “test pilot”.

    As far as “OCS”:

    It pays to be very familiar with all the speeds identified by the manufacturer, including obstacle clearance speeds that may be ‘buried‘ somewhere in the POH text.

    Understanding the concept of OCS and how to use it to fly as precisely as possible, is critical. It could also prevent you from getting bit on a check ride. Examiners expect applicants to use proper procedures, as defined in the appropriate POH/AFM, or, if something is not covered there, the Airplane Flying Handbook.

    In both the Private Pilot and Commercial Pilot ACS’, the “Skills” that must be demonstrated under “Short-Field Takeoff and Maximum Performance Climb (ASEL, AMEL)”, include the requirement to maintain “the recommended obstacle clearance speed or Vx” …. with appropriately tighter tolerances for a Commercial certificate:

    Private Pilot ACS (PA.IV.E.S10): “Establish a pitch attitude that will maintain the recommended obstacle clearance airspeed or VX, +10/-5 knots until clearing the obstacle or until the airplane is 50 feet above the surface.”

    Commercial Pilot ACS (CA.IV.E.S10): “Establish a pitch attitude that will maintain the recommended obstacle clearance airspeed or VX, ±5 knots until the obstacle is cleared or until the airplane is 50 feet above the surface.”



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