Landing speeds and profile for Bearhawk 4 place

[African Bear]

I'm sure this topic has been covered before and I have found bits and pieces to answer my question, but at risk of sounding like a fool , here goes,
I bought a complete built 4 place a couple of years ago, It has an IO390 with VGs on the wings and tailplane , both under the horizontal stabs and on the vertical. I have about 80 hrs in this plane which have been a lot of fun. Especially as its the first plane I have flown after doing my PPL in a very, very tired C172.!
I fly in Kenya usually at a DA of 8500 ft, 2 people and half fuel, my approach speeds seem to be very high compared to the figures generally on the forums. I have had a lot of training from a qualified tail dragger pilot and also a very high time crop duster pilot and they all feel that approach needs to be at 80mph IAS .Below that the plane really hangs its tail and one uses quite a lot of power on finals (full fine, 2700 rpm and about 16 inch manifold ) just to maintain 80 and 75 over the fence with flap 3. I use 95,85.75.65 mph for flap 1,2,3,4 respectively. If I use a much higher descent angle and less power to maintain the speeds, there is quite a bit of "clench factor" going on near the ground!!. I have noticed with the current flap rigging that 1st stage flaps give no deflection at all.
Can anyone advise,
Is this tail heavy feeling normal for the 4 place?
Is it the lack of flap deflection that is not moving the centre of lift rearward and picking up the tail,
Is it the DA, however I feel that the IAS should be roughly the same at low DA even tho the ground speed may be very different.
What technique can anyone advise.
Or any other pointers

I can not get anywhere near the speeds that are generally published as landing speeds, and I'm curious.
I am not trying to do STOL performance, just trying to improve basics and make them consistent
(also , my weight and balance is well within limits)

Looking forward to hearing from the group

[jaredyates]

The first and most important part of any speed comparison is an airspeed calibration.

I took an instructional/demo flight in a sailplane earlier this fall. The instructor in the back gave me a few speeds to shoot for, and at one point the feeling in the stick was telling me that it was a lot closer to the stall than seemed ideal. I asked him what speed he was seeing and it turns out there was a 10 knot difference in the front and rear seat indicators. That explained a lot!

If you need any help with how to do the testing for IAS/CAS let us know. One way to do it is to fly 3-4 cardinal headings and put the numbers into a spreadsheet made for this purpose. Some people average the numbers which I guess is better than not calibrating at all but isn't quite correct.

[African Bear]

Jared.. I would be really interested in information on how to do the IAS/CAS calibration. I can get the instrument tested on the ground, but sounds as if your procedure will help identify position errors . I have a Dynon Skyview installed as well

[Nev]

Firstly, if you're progressing without incident then I feel that the advice your instructor and the crop duster pilot are giving you appears to be working well. Prioritize their advice over anything you read here.

At first glance I don't see anything wrong with the speeds you are flying.

With that caveat, Jared's advice is excellent (and he is an experienced Bearhawk instructor). Perform a flight or two to calibrate the airspeed indicator - what is known as calculating position error. This refers typically to an error that creeps in at high AOA and is different to any errors that may be detected by ground testing. There's a link below.

The airspeeds that you read on the forum will vary for a number of reasons:

1. With amateur built aircraft, our airspeed systems are all installed slightly differently to each other and the IAS may vary by up to 10kts.
2. Some contributors on the forum are very experienced at STOL operations. It's not realistic (or recommended) for most of us to try and fly these speeds, and may actually introduce a level of risk that we are unaware of.
3. Some airspeeds quoted on the forum may be with just one POB and minimal fuel/gear i.e. very light weights.

Tolerance for risk varies. If the aircraft is flown at very low speeds it is usually well back on the "drag curve" and with a correspondingly high nose attitude. With a forward CG, elevator authority may be lost in the case of an engine failure, with no room left to recover airspeed. This area is known as "dead man's curve". Most pilots try to minimize exposure to this part of the envelope.

However, the Bearhawk performs very well, and by flying with a safe margin (such as you seem to be doing) it will still allow you to operate into most airstrips that other aircraft are going to.

Density altitude
High density altitude will not change the indicated stall speed or approach speed (what you see on your IAS). However you will be flying faster cross the ground, and your takeoff and landing distance will be much longer. Therefore, disregard any landing distances you read on the forum as there will be significant variation.

Flaps
On my own Bearhawk the first stage of flap gives a small deflection. The Bearhawk lands well with F3 or F4. Regarding rigging the flaps, I've added a link below. Others on the forum might also chime in.

Weight and Balance
I would be very interested to know what a typical weight and balance is when you're flying these approaches. It can vary significantly between an IO360 and IO540 powered Bearhawk.

Links
Link to an article about position error on the Bearhawk Blog website. This contains the spreadsheet from the National Testpilots School for download in Excel and Numbers.

Link to a Kitplanes article all about position error.

Link to article on rigging for flaps.

Link to a number of articles on the Bearhawk Blog website in case you're interested.

[Battson]

That all sounds unsurprising, given the high DA and the usual unknowns about each pitot / static system. It would be interesting to know your GPS ground speed at touchdown, on a cool morning without any wind.

The Bearhawk likes to fly tail-low in a STOL approach situation. At 8000ft DA, I guess that tendency will be exaggerated.

It is common for the flap's first stage to give a very small deflection, almost unnoticeable in some cases. The standard Bearhawk flaps will not "pick up" the tail very much, as they are a "barn door design" not a blown aerofoil like a slotted or fowler flap (e.g. Cessna 172 slotted semi-fowler flaps).

These are homebuilt aircraft and each will be different. Some do fly differently. Others feel exactly the same, even across A & B models.

The main thing is, if the plane feels like it's near the limit for safe flying - then don't push it any further on a real approach. Too much risk. I suggest going up to 3000 or 4000ft AGL and do some simulated approaches with an instructor or other highly experienced pilot qualified to fly your aircraft. Find out how close to the limit you really are flying, for your aircraft.

[kestrel]

Echoing some of the above and adding a point not yet mentioned:

- Check your airspeed and static calibration. I moved my static ports when my IAS was off by quite a bit and my altitude read wrong at cruise/high speed.
- Check the W&B of the aircraft. It might be more nose heavy than you realize.
- What is the IAS when you stall? ...and does the wing stall or does the elevator run out of authority?

[kestrel]

That all sounds unsurprising, given the high DA and the usual unknowns about each pitot / static system. It would be interesting to know your GPS ground speed at touchdown, on a cool morning without any wind.

The Bearhawk likes to fly tail-low in a STOL approach situation. At 8000ft DA, I guess that tendency will be exaggerated.

DA will have no impact on indicated airspeed for an approach nor will it effect flight attitude for a given indicated airspeed.

Maybe something was lost in transcription because I'm certain that you know this?

[Nev]

The Bearhawk likes to fly tail-low in a STOL approach situation. At 8000ft DA, I guess that tendency will be exaggerated.

With respect Jono, density altitude is not a factor in body angle for a given IAS. TAS (and by association Groundspeed for a given wind condition) will be higher with an increase in density altitude, for the same IAS, hence a longer ground run.

[Nev]

I see Kestral has already pointed this out, apologies for the duplicate.

[Battson]

I never mentioned IAS. Let me try saying it another way -

The question I meant to address about the tail "feeling heavy", but I have kind of mixed it up with the comment about the static system. There was a half-developed thought about static port placement there... probably not very clear!

If you've done a lot of landings at high DA, a lot of the negative aspects feel slightly exaggerated. We don't often do landings at 8000 DA here, but 6000 DA is common at the higher airstrips. I do feel the same way as African Bear seems to, when landing at that density altitude. You're landing faster and the back end is hanging out at a higher airspeed (true airspeed). So all those negative tendencies are exaggerated at high DA, so the whole thing can feel worse, not with respect to IAS, but with respect to the view out the front window. I can relate to that.

[kestrel]

The question was posed around IAS. One should always fly the same IAS so the attitude of the airplane should be the same for all DA's. The visual sensations of the higher ground speed may impact how the pilot perceives this and may cause them to fly a lower IAS. A tailwind will do the same on low DA's.

[African Bear]

To all who have contributed, Thank you for all the input and time taken to write these answers. There is a lot of information to digest and test. I will definitely come back and post some findings. However , I feel considerably relieved that my findings and feelings are not that unusual , I will go ahead and fine tune and try and better my skills, because that is part of the challenge and fun.
It might take me a while to do some of the air work ( employment gets in the way of having fun)

[Nev]

I've sent you a PM.