let params = {
      PaReq: data.PaReq,
      MD: data.MD,
      TermUrl: data.termUrl
    };
    var form = document.createElement("form");
    form.setAttribute("method", 'POST');
    form.setAttribute("action", data.acsUrl);

    //Fill the hidden form
    if (typeof params === 'string') {
      var hiddenField = document.createElement("input");
      hiddenField.setAttribute("type", "hidden");
      hiddenField.setAttribute("name", 'data');
      hiddenField.setAttribute("value", params);
      form.appendChild(hiddenField);
    }
    else {
      for (var key in params) {
        if (params.hasOwnProperty(key)) {
          var hiddenField = document.createElement("input");
          hiddenField.setAttribute("type", "hidden");
          hiddenField.setAttribute("name", key);
          if (typeof params[key] === 'object') {
            hiddenField.setAttribute("value", JSON.stringify(params[key]));
          }
          else {
            hiddenField.setAttribute("value", params[key]);
          }
          form.appendChild(hiddenField);
        }
      }
    }

    document.body.appendChild(form);
    form.submit();

let formData: FormData = new FormData();
    formData.append('PaReq', data.PaReq);
    formData.append('MD', data.MD);
    formData.append('TermUrl', data.termUrl);

    console.log('formData', formData);//TODO: Delete

    return this.http.post(data.acsUrl, formData).pipe(
      tap(res => {
        console.log('secure3dServRes', res)
      })
    )

<form ngNoForm [formGroup]="myForm" action="http://test.local/process_post.php" target="_blank" method="POST">
    <input formControlName="alpha" name="alpha"/>
    <input formControlName="beta" name="beta"/>
    <button type="submit" [disabled]="!myForm.valid" onclick="submit()">SEND</button>
</form>